Stick with the 120, rather than a gas engine. The Ultimate is a lightweight plane that probably wouldn't do as well with even the smallent and lightest gas engines.

Who said "gas is the only way to go with smoke"? Several popular smoke systems can be successfully used with 2 and 4 cycle glow engines, But, remember the extra weight of the smoke fluid and pump, batteries, etc. That'll mean lower levels of performance on an otherwise great flying model.