Checked spar sag with dental floss on front spar, Removed sag with a 2 x 2 support under #8 rib with a T nut installed in bottom of 2 x 2 for adjustment.
Installed plumb bobs at #2 and #14 ribs to adjust rear spar with plumb bob's at the inbroad and outbroad ends of rear spar. You want to align ribs center line with plumb bob vertically and adjust rear spar to plumb bob string so they are the same measurement on both ends of rear spar (inboard and outboard) Mine measured 2 3/8.
