Bryris,

I had athe same thing happen. My LHS owner let me borrow a simple, home made sanding tool to beautifully correct this problem. He had a 10-12" flat board about 3-4' long with another board not quite as long or wide attached lengthwise at the edge at a right angle like a backstop. Then on the short end was a groove that a third board could slide back and forth in. He used a simple peice of angle iron to hold this board at a right angle when in the groove and glued sandpaper to the other side of the sliding board. To use it, one half of the wing is laid flat on the board and held firm against the backstop with the wing center-end against the sand paper. Slide the sand paper board back and forth for a square wing center. The same thing is repeated for the other wing half but this time with the dihedral gage clamped in place under the wing. The result was a perfect fit in less than 5 minutes. I was lucky because I could borrow the tool, but material cost would be next to nothing at the home store and they could probably make the cuts for you.

I hope you can make sense of my rambling and try this out. You will like the way it works.