RC/Ron, I'm not exactly familar with the OS 40FP, but I am familar with the 40FP controline version, a well loved engine. You will not have as you say a "rocket". But if it is in good condition, it's a good motor. Have you test run it lately? I think it would be a fine motor for the Tower Trainer 40, if in good condition. Just from what I can tell from flying mine and my experience with a similar sized plane the Avistar, I think a Thunder Tiger GP42 would be a fine motor, just from my experience. Many are going to tell you, go with a 46/47. I've got a GMS 47 in mine, and it has plenty of power. If you're strapped for cash, it'll work. If you're wondering what might you want sometime down the road in it, try to get a 46/47 in it. But if your 40FP is running good, it'll work. I loved how my Avistar flew on just a TT GP42, had a blast with it, even in windy conditions.

South Bend? My folks grew up there. Grandfather had a floral shop there on Washington Street. Interesting.

Good flying to you.

Tom Niezgodski (name before my folks changed it)