Originally Posted by chuckk2

The Alpha 40 I have was designed to accept an engine or motor
The recommended motor was an E-Flite 25. (The lower KV version and a 4S 3300mah Lipo is what I used with a 60A ESC)
The higher KV version would use a 3S lipo.
Obviously, higher voltage means less current, and slightly less IR loss.
The 4S Lipos I used weigh about 14 Oz.
One problem/concern was that the Alpha 40 I have ended up being tail heavy.
Rather than add a bunch of weight, I ended up relocating the wing about 1 inch
back from the designed position.
Knowing that, I'd recommend using an E-Flite 32, mainly for the added weight.