Everyone has their opinions on power. For training and putt putting, my opinion is that an OS 55 is way too much. Mine, at 6 lbs even, flies perfectly for those purposes with a 46LA. See post above. If you don't know the 46LA, it has about half the power of a 46AX. Maybe less than half.
Beginners over-control, so I like stick movements that are not very sensitive. With such a large engine the throttle stick is bound to be sensitive. That's why I like modest power for training. Tell the student to bump up the throttle 2 notches and he gets a little more power. It's safe.
Jim