RE: Holly Smoke engine choice
I got used to mine with a Como(ST) 40 with a muffler, and it flew great. Later I used a Como51 with a pipe, fast as I wanted it to go. Deltas are fun and look cool in the air. If you go that route just use the same brand of engine that will drop in the next size; or else you could use the ST 51 and under prop it.