Another area where shims are required is between the aft end of each interior flap rib and the lower skin’s J-channel. This is one I really can’t understand…why doesn’t Van’s just make the ribs long enough? Ok, enough grousing already.

One minor catch here…the aft-most hole in each rib’s lower flange isn’t drilled. That gets done by using the corresponding lower flap skin as a drill guide. Without a cleco to hold them together, the rib flange and skin must be clamped together tightly before the rib’s rear tab and shim are match-drilled to the J-channel, pulling the tab into the proper position. Clear as mud, right? Anyway, I used a small piece of plywood and a clamp to pull the flange in place, and another clamp to hold the shim in place as it and the tab are match-drilled to the J-channel. The shim gets trimmed to length after drilling.