Tom, the TT .36 is a Pro (BB). The GP .42 is a bushing. Power to weight, the .36 is way ahead of the .42.

You would be better to put a Pro .36 in this plane than a GP.42, and IMO, even better to use the Pro.46. You can always throttle back a .46, but you can't squeeze any more power from the .42, you're just stuck with what you have. And a BB engine will generally last longer than a bushing.