OK, my first suggestion probably won't appeal. Ditch the 200mm cranks. I've never been convinced by the notion that big guys would benefit from long cranks, because it seems to me that maintaining a similar cadence with long cranks requires higher leg speed, and if you have to slow the leg speed to compensate for the higher cranks, you may as well have just stayed in a higher gear to begin with.
But if you want to continue the experiment, then my answer would be rollers. There's nothing like them for promoting smoothness.