09-14-2011:
I understand what a twisted wing can do during flight from my RC model flying. To make sure there is no twist in the wing before final drilling the holes, I bought plumb bobs and a more acurate leveler from Harbor Freighter Tools today. Measured the distance between the plumb bob line and rear spar, the initial reading showed a difference of 1/16". After re-clamping the rear spar, I got the difference less than 1/64". The wing should be straight. I will do the drilling tomorrow, it will take some time, just too many holes.
Wing root is checked for levelness
Wing tip is checked for levelness
Rear spar is clamped at the root side after levelness check
Distance reading at tip side, 1 20/64"
Distance reading at root side, 1 19/64"