Any wing around 36" span should work reasonably well.

My wife has decided to learn control line, and she's still at the point where you crash almost every flight.  One thing that this has forcibly taught me is that electric motors have much more fragile shafts than internal combustion engines.

Until someone comes up with an electric motor with a shaft big enough to land on, I suggest that for training you adopt a "batteries front" layout (because they can smack into dirt without bursting into flame) that protects the motor.  This is what's on my bench, although I haven't had it in the air yet.  Just make sure that you remember to mount the bellcrank out far enough that the pushrod stays out of the prop -- if you look close you'll see the scar on the wing where I ripped off the bellcrank mount and redid it.