You must think in three dimensions both the cord and the wing thickness is tapered. Your support should be following the angle of the wing taper (parallel with the training edge line) and NOT parallel with the main wing spar. If the support is in the correct spot the center line of each rib will line up in one straight parallel line. Each rib is a difference thickness and therefore for the centerline to be at the same height from the building surface the support must be angled to hit the correct point.