Nearly completed front rib angle drilling. I noticed that after drilling on rib angle for rib #3 that the second hole (top and bottom with equally spaced 7 holes) it placed the second hole too close (4mm only, need 6mm) to the edge of the 6W11-11. Therefore I drilled another hole about 8-10 mm further into the 6W11-17. I don't like the holes near the edge (I didn't drill through 6W11-11 yet, only 6W11-17, so i think i'll get another piece of 0.040 L channel and replace it. The same issue on Front Rib #2 so before drilling it, I drilled 10mm, 30mm (still only on 6W11-17), then the 3 center holes in the original pattern. Lined up and drilled rear channel to rear ribs like HomebuildHelp suggested, all with final drill holes.