Spent several hours work with my friend Ross on the rear spar. Riveted in one of the doublers, and worked on the one of the wing rib attachment assemblies. Discovered a possible plans error on page W15, it calls for a 1 inch screw, but that seems two short as it does not allow for 1 1/2 threads to be exposed above the nut. Looks like it needs 1 1/8 inch screw. Will post on build forum and contact Sonex about it.