ORIGINAL: doctorgo
In regard to the wing: File the slot into which the "tang" at the wing's leading edge fits, deeper, a little at a time, until the the contour of the top of the wing matches the saddle in the fuselage. There will be no incidence problem.
Also lengthen the slots in the wing where the aileron rods protrude...there's not enough clearance for full aileron movement.
I located both tail servos in the aft location that's provided and the engine at 5 9/16 inches from the firewall. (Forget the spacer.) No extra balancing weight was needed with a .91 2 stroke-cycle engine. Don't beleive the weight stated on the box; the completed model will weigh near nine pounds.
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I am going to cut servo cavities in my wings and then use the old pattern trick of sharpening a piece of brass tubing so that I can cut a tunnel through the foam and into the servo cavity from the wing root. The tubing has to have a large enough outside diameter to permit passing the servo connector through the tunnel. This is easy as pie. Toss the aileron torque rods in the trash. That is where they belong.
I have a BME G90 gas conversion that I might try, although a Saito 1.25 would probably be the best choice for light weight and good power.