Today I started installing the aft root rib, and stuffed it up. First I made a device to keep a hole in the aft spar at the correct distance from a hol in the main spar (19") as per plans. (See picture). Then I clamped the aft root rib in place (incorrectly and started drilling). As you can see in the picture the root rib was positioned to far aft, therefore the holes on the forward side are too close to the edge. I will have to re-make this aft root rib unfortunately...