Thanks for all the input!! I bought a Jammin .28 after all the talk here. It's just starting to break in.
As far as "too much" power goes, I could see that on a smaller track, as the motor not being able to wind up. But I am on a huge track.
I went up 2 or 3 teeth on the clutch bell to mellow out the bottom hit. Plus gearing it like this compensates for the lower RPM's of the .28 vs .21, to get it up to crazy top end speeds. I think I'm going to be super happy. The bottom end rulz!!
Thanks forum!!