well, a TT 46 is excellent, but I have a Power Force 46 and it now pulls m dads second plane, a low wing sports around at an insane speed.
They are cheap as well.
But what ever you dont get a 40 because they are only good for a trainer, nothing else so you will need to buy a new motor for your second plane, and 46ers arent that much more.
Fly-guy