MartyPetriSr,
I am unable to reply by e-mail so I am answering here. I am not sure which F15 you are building. If it is the simple I have no build guide for it. I used a B21 motor on mine. It was under powered when I placed it in the mid wing as instructed, because I had to go to a 6 inch prop. I moved the motor to the rear with the 8x4 prop and it was fine. I never finished the F-15 full body build. Still out in the shed in parts. AJ built one, I think his was EDF. I am attaching the build guide for it, if it is the one you are building. The build guide is for a pusher. It has charts for different motors. I think based on the chart the B21 would have worked on it. I just never got around to finishing it. It was above my skill when I started it and I never have gotten back to it. I have a lot of plans downloaded and there are a ton more I want to download. If I can help get you a plan I will be happy to post one. I have been so busy since the first of the year I spend very little time building or flying. Miss it a lot, hope to be able to get back into it more one of these days.
I did get a Micro Mosquito Heli to fly in the house. Having a blast with it.

LT