I was fitted to my road bike by the LBS shop owner, and then replicated the pedal spindle-to-saddle height on my MTB. The MTB has a higher BB so that means the saddle itself is higher off the ground than on the road bike. Similar thing would happen on a folder with small wheels I would think. If you replicate spindle-to-saddle of other bikes, then the saddle itself will end up lower to the ground. You would also have to be more careful about crank arms or pedals hitting the ground if you pedal through a turn, assuming you use the same crank arm length as on normal bikes.