Finished up work on the center section spar. Cover supports drilled to spar, holes enlarged as needed, snap bushing holes upsized and installed. The smaller cover support gets a angle stiffener on the opposite side that is flush riveted to the center section and has nut plates that the support screws into, I assume so you can easily take it off for wire runs, maintenance, etc. once everything was cleaned up, primed what was needed, items were riveted and or bolted per plans. The two center spar sections were temporarily placed together with the spacer tubes in place to make sure it was ok. Seemed good to me, oh and btw, the spacer tubes are already made to the correct length. Look in your wing kit hardware bags.