I was actually recommending the RimFire .32 as a suitable trainer motor for the Tower Hobbies Trainer 40 ARF. The Tower Trainer 40 will fly really well with the O.S. 40 LA glow engine, which is a bit weak for a .40 cu in engine. The RimFire .32 will produce more than enough power to fly the Tower Trainer 40 ARF well, and is recommended for sport flying with planes up to 6.5 lbs.

The gap in the RimFire line jumps from a .32 replacement to a .46 replacement. Unless you're planning on putting the Tower Trainer 40 ARF on floats or carrying camera equipment on it, a .46 motor is overkill for the airframe.