Van's calls for leveling the airframe forward and aft, and left to right to measure the wing incidence angle. I made a spacer at 2.79 inches which is placed under a carpenter’s level at the rear spar rivet line, the front is place on the main spar just aft of the top skin overlap. The ideal wing incidence angle is determined when the carpenters level is, well, level when using the 2.79" spacer as specified.
While the wing incidence angle is important, more important is the edge distance of the rear spar to the fastener (bolt) of 5/8 inches. After I determined the left and right wing have the same incidence angle, I checked the rear spar placement in the spar tab that traverses the fuse.