I've had twitchy bikes before, and simply got a LONGER stem and made sure the stem was below my handlebar by at least a few inches. say a stem from 100 to 120 is OK, but of course this must mean your reach won't be throw completely out of whack. Then try to put the seat a few inches behind the BB, at a minimum. Maybe even raise the seat very slightly (if you never got a fit that is...i mean like 1/8th inch). Ride this for an hour, and if it feels bad, keep adjusting. my bike does have a relatively long wheelbase. a lower BB is good, but that's harder to change (new bike). gl