Hi, This was our club plane for about a season. I've instructed on it a bunch of times. In general, I recommend a ball-bearing .46 engine... This plane will fly great with a .40, but for reuse value, or if you might put it on floats, a BB .46 will keep you happier, longer. Not a bad trainer. If $$ is an issue, there are plenty of inexpensive 2-stroke BB .46's around... They all can be make to run beautifully.... GMS .47, Mecoa .46, Magnum .46 or .52 .... of course if money is no issue, there's always O.S.

Just one man's opinion.
Best of Luck,
Dave