I have not had any experience with the TT motors... been a loyal OS and Saito man, but I think you have talked me in to trying one of these TT's.
Yep, I was a die-hard OS fan......until I bought that OS 46 LA you see on the Stickit. That engine soured me on OS, and convinced me to try a Thunder Tiger.......and I'm glad I did! I now own several TT Pro 46s, a TT Pro 61, a TT Pro 120, a TT Pro 36, and several TT 42 GPs. I've been very pleased with all of them.
The kit calls for a 25-35 size motor. Should I go with the TT-36 or the TT-42 GP??
The TT Pro 36 and the TT 42 GP weigh almost exactly the same, so weight isn't an issue. I preferred the TT 42 over the TT 36 because the 42 has slightly better throttling characteristics, especially in the mid-range where the 36 tends to load up.
I will most likely use the stock muffler for a while 'till I'm ready for the MCP.
The stock muffler will work fine, but once you try the MCP you're going to kick yourself for not trying one sooner.