Just as I thought, I was able to change a FF's movement cost to 0.10 and a BC's to 0.8. May try later to see what's the lower/upper end of the movement cost range.
ADDENDUM: well, I don't know what the upper/lower limit is, but I took a BB up to movement cost 30, took it forever to get moving, and a FF down to movement cost 0.01, top speed of 30.53 for only 0.3 power. It also took off like a rocket, even though I hadn't touched the acceleration rate.
I sorta remember reading somewhere that movement cost figures into acceleration at some point, but I thought that point was after 20 (the example was that a FF and a DN will accelerate to 20 at the same rate, but the FF will get to 30 faster than the DN would), but I guess it's a more complicated relationship.
So, the game isn't just locked into the SFB movement costs (1/5, 1/4, 1/3, 1/2, 2/3, 3/4, 1, 1.25, 1.5, & 2) and can use any number. Hmm, I've always thought the D7 had the wrong move cost and power ratio...