Nothing wrong with using a good 46 sized bearing engine on a trainer. The extra power is well worth a "lot" of times while training. On SK engines, I bought a 80 size to try because of the price. It has never run well enough to even do a high speed taxi, let alone attempt a take off. In this case you do get what you pay for!! I pulled the engine and replaced it with a Tower Hobbies 75 engine. ITs inexpensive as well but its the best engine in its size range even against OS or TT engines regardless of the higher price engines. [8D]