Shortening wheelbase for polo bike (MTB)?

My polo bike is a Specialized Rock Hopper, and I think it's pretty perfect for the job, except for the fact that it's really long. 104 cm wheelbase at the moment. I understand that should be under 100 for the sort of handling that polo require, but that's such a major change I'm afraid I'm going to screw up the geometry. Can anyone comment on this? Or on how majorly altering the rake/trail will change handling for the better/worse/weirder? I'm a little fuzzy on all that, and on exactly how far I can push it.

Two trucks.......... Smash!

I think edscoble converted a MTB, adding horizontal dropout which should in your case possibly bring in the rear wheel a good inch or two depending if there is clearance issues or not.

I'm halfway through doing this. Chainstays shortened by approx 60mm and headtube angle increased from 72.5 to 74deg. I'm doing the shortening of the rear triangle myself but forks will probably be built for me.

Changing the fork will hardly impact on the overall wheelbase. Apparently 60-65mm trail is ideal iirc. Changing the fork can also improve the manoeuvrability but there are other factor to bring into play. Length of stem - a short stem is always going to be more 'twitchy' than say a 100mm stem. Weight balance - simply changing the height of the contact points can change how a bike handles.

Wow, that's something I hadn't considered. Obviously not worth getting out the braising torch for my little rock hopper though. Out of curiosity, wouldn't it be more practical to just get a different frame?

Probably, but when the build of this bike cost me £100 why spend £200 on a new frame unless you're getting exactly what you want. My frame is cheap and heavy which makes it easier for me to adjust. It's not worth paying someone to change a frame for you because of the cost.