While either engine will fly the trainer nicely, I think it is a waste of a fine piece of machinery. You may even get a chuckle or two at the field. It's sort of putting a Corvette engine in a station wagon or 1/4 scale servos in a 40 size airframe. The Saito is a great engine as well, but in a trainer you will be taking the risk of ruining a good engine. If you must go for a 4 stoke, I would buy a Magnum. They run great and are price freindly. Sorry for my opinion, just a thought.