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.