I'll throw out an idea. I'd look at a mega 16/15/5, a TP 3s 2100 lipo and an apc 7x5 eprop. I'm using this on a Great Planes Slinger with good results. I like the balance between speed and thrust. I think that the battery would fit. This motor or the speed 300 can be mounted several ways. It can be bolted in from the front using a firewall, you can use a clamshell mount and either rails or a glow mount, or you can roll a motor tube from 1/64" ply and mount the tube from the firewall behind the motor.

John