The GP F-15 will be underpowered with a 40 sized engine. It was the first kit I built after my trainer. I put an OS 46 on mine and was disappointed in the performance. After flying it for a season a friend suggested putting a tuned pipe on it. A Mac tuned pipe gave me about another 1500 rpm and really made the plane come alive.

I had a blast with the plane and flew the crap out of it for 3 or 4 seasons, probably 300 to 400 flights. It's not very aerobatic, but can slow down to a crawl doing a cool nose high carrier type landing.

The plane is as heavy as a lot of 60 sized planes but I wouldn't recommend putting a 60 on it because you already have to add a bunch of tail weight. I'd recommend a 50 engine with a tuned pipe if you want it to fly like a jet. Put the battery as far in the back as possible. I made the back plate on the fuse removeable and put the battery there. I still had to add a few oz. of lead.

Mine has been sitting in my basement for quite a few years. Maybe one of these days I'll dust it off and fly it again.

Joe