For someone (not me) using a 9" mallet, who has some trouble with rushing and hoop running, would you suggest a longer mallet head (10"?) could make a difference?  And do you think that a jump from 9" to 10" is ok, or would it be better to go 9" to 9.5", or conversely 9" to 11"? 

1. It will twist less on an off-centre contact with the ball.
2. There is more visual feedback to the striker when they are casting to help them keep the mallet swinging in line.
3. Often with a longer mallet there is also a greater proportion of the mallet's weight in the head, which leads to a more pendulum-like swing, as it makes it harder to manipulate the mallet.

Both points 1 and 3 are about rotational inertia being increased, albeit about different axes: one through the ball-mallet contact point, while the second is thru the shoulders (or wrists or elbows depending on your technique!)

Be careful with the big jumps in head length, as there is also a bit of technique change as you get longer mallet heads — the swing generally needs to get flatter, and the stance sometimes changes to accommodate the bottom arc of the mallet swing. When I was playing with a 9" head I found a 10.5" excellent, and couldn't effectively hit a ball with a 12" mallet. That said, my first outing with my shiny new 10.5" mallet (and a significant change of grip), I destroyed the end of A baulk on lawn 8 at Cheltenham!

For a relatively new player it can be very hard, and thus disheartening, to use a significantly different mallet, and often the mechanical advantages of having a longer head are outweighed by the coordination difficulty the player has in swinging the new mallet.

I guess the bottom line is ... get the person to have a go with different head-length mallets, and see what works best for them (though obviously this changes over time).

This could be viewed as a disadvantage as well, depending on one's stroke.  While there are those who espouse the speed of forward swing should be a mirror of the backward (i.e., gravity only), I'm not one of them.  Thus, the forward swing takes less time to occur.  For this reason, any twist in the backswing will be harder to "undo" on the forward due to the higher moment of inertia of longer and peripherally weighted mallets.

There are also disadvantages to longer heads.  It may be harder for shorter players to make the required swing arc.  Stop shots are also harder (or not as effective) given the shallower face angle.  Having a long head in a hampered shot is very disheartening, when you know you could have made the shot with a shorter head.

Like most  things,  it will be best to try various heads and evaluate on a case-by-case basis.

I went up from 9" to 12" by making a new longer headed mallet for each season — a steady change worked for me.  I tried a longer (than 12") head but found the general clumsiness too great.  I recall Stephen Mulliner and John Walters both tried mega-long heads (16" or so?) in the early 90s — but didn't stick with them.

You get used to the extra ankle bones quite quickly!  Once or twice a year, usually early in the season, I trip over the head as I walk out of the stance — the head then twists and catches my (for some reason) left ankle a treat.  So during the season I usually seem to have two ankle bones on my left leg!

I don't entirely agree with a couple of Paul's points: I didn't find stop shots got more difficult with a longer head (indeed I think it's one of my strengths) — but perhaps my technique improved in parallel with using a longer head;  and while there are some hampered shots that become more difficult, there are others that become easier — for example, when you've just run a hoop by a 4 or 5 inches, you can prod the ball with the mallet through the hoop, when other people are having to try tricky sweeps and so on.

There are always exceptions to any rule in croquet, e.g. Greg Bury, a fairly tall player, always played with a very short mallet head and roqueted extremely well.

Big rolls and splits can be a bit more difficult to control with a longer mallet head, but perhaps paradoxically, a long head seems to suit long rushes very well.

A one-inch increase should be quite manageable.  A two-inch increase would take longer to get used to.

The face angle (from vertical) must be less, which I think most people believe to be detrimental for a stop shot.  Relative to a 9" head, the maximum angle decreases by 10% (10" head) or 25% (12" head).  Whether that makes an appreciable difference in stop shot ratio is certainly open to debate and experimentation.

I performed a quick & dirty experiment with my mallet clamped to a broomstick suspended over a couple chairs.  While hardly rigorous and there are various issues one could pick at (and that seem negligible to me), it is what it is.  Perhaps someone with access to a swing machine can conduct a more rigorous test.

So what happened?  A croquet stroke with a vertical shaft at impact achieved a distance ratio of 3.5.  Moving the mallet pivot point back 4" (causing the shaft to lean backward approximately 6° at impact) achieved a ratio of 8.4.  Same mallet, same backswing distance (approx. 12"), same balls and orientation, same surface, same ruler. :-)

Again, it's taken longer to write this email than it took to set up and perform the test, so it wasn't the most scientific test ever conducted.  However, it does suggest that an angled shaft may be an important component of a good stop shot.  Since the head length limits this angle, it also suggests that head length may also be quite important.

I normally play with a 12", but had occasion to try a 9" with measurably better stop shots.  Whether that was due to the shorter length or less total weight or the weight distribution or xyz I couldn't say for sure.

However, I have also seen videos of others with short-headed mallets whose stop shots are much better than mine.  Clearly, then, it must be the equipment. The golf industry learned this long ago — why does croquet insist on ignoring the overwhelming evidence?  ;-)

I started playing with a 9"  the same as everyone else at the club probably did.  I quickly changed (within 12 months) to an 11" and then up to a 12" some twelve months after that. I have a 34" shaft, I have tried with a 36" but I'm not quite so accurate with it and it tends to make me a little more 'wristy'.

Bruce Fleming (my husband) is 5' 4" (5' 5" he says) and has played with a 12" mallet head for as long as I have known him.  He plays with a 32" shaft.

I believe it could be argued that we are both pretty accurate and successful players.

I am the Queensland Agent for RPM mallets, and a very active coach, so get to see see lots of players both new and experienced.  I would honestly say that no one I know has ever appeared to have an issue with moving straight to an 11" no matter what they have used previously.  I never advise less than a 10.5" (if asked for advise), and try to encourage new players to start with an 11" unless there is some sort of physical reason why they should not.

Bob Jackson is not a tall man, nor does he have a particularly lengthy shaft, but he uses 12/13/14" mallet heads with great success.

Lots of Golf Croquet players have told me they prefer a shorter head but I don't have sufficient knowledge about Golf Croquet to offer an opinion on that one.  I think it strange though because my single ball shots are much better with the longer head.

Some seem to manage quite well, but my experience suggests that taller people with longer legs and arms can adjust to the longer head with less difficulty, because they naturally swing the mallet in an arc that has a longer radius and therefore the mallet is for a longer time travelling almost flat, parallel to the ground.

Shorter players can learn to develop a flatter swing, but with some it takes time.

Bob Jackson has always used a sort of "short-arm jab" rather than a real swing when roqueting, and if mallet heads continue to increase in length, that is what we may all end up having to do.  (I think he uses a left-handed grip and a right-footed stance, which to some extent necessitates such an action.)

While, as Liz Fleming pointed out, there were some long heads in Queensland in the mid '90s, my 12" Jacko was still pretty rare.  I tried playing with an 11" RPM five or six years ago, but soon went back to a precisely weighted 12" head (custom made by the good Mr. Fleming).  

So, as a relatively new player - 2 1/2 years — I switched from my 10" mallet to a 12" peripherally weighted mallet — and the results have been mixed.

I find that the positioning of my hands (Solomon Grip) is more critical with the longer mallet head.

I've adjusted my stroke somewhat to accommodate the different characteristics of the peripherally weighted mallet, but find that when casting, the mallet in fact exacerbates the rotational tendency caused by the smallest misplacement of my hands/grip.

I'm very conscious of this — and the variable results — sometimes great — other times just missing from the same distance because of head rotation — has somewhat sapped my confidence in going for roquets.

I'm thinking of reverting to my 10" mallet head - although my natural stubbornness compels me to persist — especially as I shelled out good money for the mallet.

Dunno what the answer is — should I persist — change my grip — revert to the old mallet ...