It has been some time since you posted this but I can share my experience with this Gee Bee.
First and most important is that the COG given in the instructions is way too far back. I believe they say something like 65 to 70 mm back from the leading edge. The plane is absolutly uncontrolable at that position. The proper COG is 38 to 40mm.HUGEdifference.
With proper CG and enough power this plane flys like it is on rails. I will share my setup with you.

Motor: Exceed Monster 10
ESC: 40amp Exceed Volcano Series
Battery: 2650ma 20C 3S (mounted sidways against front bulkhead in fuse)
Prop: APC 10x7E or 11x7E
3 servos of your choice

The most important part- 1/2 pound of lead attached to the motor mount to achieve proper CG.
I also had to modify the landing gear. The hard points in the wing loosened up right away and the supplied gear are so short that prop strikes are unavoidable. I made longer legs (4" from wing to axle) and angled farther forward.

This little plane is fast and has very high wing loading so it has to land fast. My all up weight is close to 4 pounds.
She will fly but this plane is not for the faint of heart. Just as crazy to fly as the real Gee Bee R2.

Matt</p>