Skip the GP .42 and get the Thunder Tiger .46 Pro or OS .46 AX. Yes, it's more money, but those engines are strong enough to fly any plane on the market that's rated as a .40 size plane later on. The GP .42 is a fine engine for a trainer or for an older lightweight design that was genuinely meant for a .40 engine.

And do listen to John about the wheelpants. Actually, listen to John every time he says anything. But on the wheel pants topic, you will need to keep your trainer simple. Give yourself the best chance of having good ground handling and trouble free flying days so you can learn.