my ss/fg mtb frame is a little small for me, i run around with the seat jacked up pretty high on it and run a fairly short stem (i think its a 90) and have no cramping issues at all... i just kept the bars down low (0 degree rake on the stem, and only one short spacer on the steerer) and i mounted some bar extenders just to the inside of the brake lever(s) giving me a nice comfortable riding position most of the time when i dont need alot of torque...
i've had wierd nasty cramping sensations riding bikes fitted to other people... even family members that are not sized that terribly different from me... but i must say my kona never let me down in the comfort department and i really like the ample ball room when snow and trail riding
-pete