Hi Jo,
Make that fuselage wide enough for a commercial tank with the maple motor mounts long enough to touch the wing sheeting.
Make it tall enough to set the engine about 5/8ths of an inch higher than the centerline of the wing, and the stabilizer 1 1/2 inch above the wing centerline. I mount engines inverted, no problem.
Make the spinner ring to leading edge long enough to mount the tank and engine with a little space between, 1/4 inch is enough.
The wing trailing edge (flaps removed) to stab trailing edge (elevator removed), which is known as hingeline to hingeline, should be around 15 to 16 inches. If the trailing edge is fixed (no flaps), 14 to 15 should do fine.

I think these should do well for a decent first full body stunter. I would use the PT-19 wing and tail, the Flight Streak has a thin wing and is a Slow Combat model and flies too fast for any serious precision aerobatics.
Chris...