John, you might get a kick out of this. Here's an extreme multi engine plane. It started as a Tower 40 trainer and my friend kept adding motors, one at a time, until he got up to 7 engines. I think the 3 engine version was his favorite. The motors were whatever he had and some loaners from friends, all used, and ranged from .25 to .40 size. Needless to say, he is a very experienced multi engine pilot and quite proficient at flying with an engine out. He came up with an engine pod with a throttle servo and a tank that allowed him to make any trainer a multi engine trainer. All motors were run a few minutes on the ground and run slightly rich.