I measured 3 inches from the firewall along length of the side skin stiffeners and made a mark. I removed the stiffeners and clamped them to the bench along with the blocks and used the blocks to match drill the stiffener. The bench acts like the skin and holds the stiffener and block flush on the skin side. HOWEVER, I didn't clamp well enough and got a couple holes off center. So be careful and do it good.
Then I made 2 optional positions about 1 1/16 inches apart. This is basically 1/3 rd the distance between the first two holes.
II'll build this in the most forward postion, but the short postions are nice to have options for the pilot who may be flying this airplane 50 years from now.
