I'll tell you that my OS 70FS Surpass flew my PT-60 with plenty of authority. Most ARF .60-size trainers are much lighter than the PT-60 I built, and generally recommend .46-.60 2-strokes.

Don't worry about using such an expensive engine in a trainer. Unless you crash full-bore, nose-first into something hard like asphalt or a large rock, the engine is the last piece that gets damaged on an R/C airplane. Most of the time, the engine hits soft dirt and the airplane crumples around it. It's a great, friendly engine that will give a beginner far less grief than some of the lesser two-strokes.