Although I have no direct experience with multi-speeds, when my brother was on team 900 in '03, they made a two speed. It would have been great, but they messed up their gear ratio calculations, the high speed was way too fast and nearly uncontrollable. Beware of incorrect ratios. Mind you, I'm not one to talk, the four speed double dog design I was pushing at the beginning of this year had a 4th gear with a speed in excess of 20 ft/s!
(It got canned due to budget and lack of machining capability)
PS Shouldn't this be in Technical Discussion?