RE: Installing Retracts
If it were mine, I would go ahead and cut the spar so the gear will fit in the correct location. Be sure to keep a radius on the cut-out area to prevent a stress point. Then cut and glue doublers on both sides of the spar. Do the same at all the sub spars as well. Maybe even add a little carbon fiber to the top of the spar before sheeting the wing, and between the spar and added doublers. If installed correctly, carbon fiber can add a lot of strength without much weight.