I have a Sport Cap with an OS 50SX and this is working out well. Didn't need any extra weight to balance ( I have a 1400mah battery under the fuel tank) One of the "guru's" at the club took it up the first time - said it has plenty of power. Unless your looking for extreme performance consider this engine, it fits the stock mount. I did cut the cowl a bit aggressively to make sure I have good air flow, but the same concern exists with the other engines also. Hey.. good luck
DickB