I personally never liked the feel of the car with the two-piece mount, rear end doesn't feel as locked down, so I only run the one piece mount, albeit with differeing centre mounts depending on situation/track.
Even with my stock car thats the same... as for changing gearing, I agree it's a pain on the one-piece with big pinions/small spurs, but not that much of a chore. Take the top deck off, undo the centre axle mount, then move the motor back and forth until correct mesh... then do the front motor screw up, pop out the spur, and do the back one. Easy enough really
