The ribs are square to the spar and are straight front to back and top to bottom.

The issue is that when they are set at the correct dihedral the upper spars touch while there is still a gap of about 1/8" on the bottom spar.

What is the point of having a rib guage if it doesn't work - or if the instructions do not tell how to use it!

From my experiences as the wing is built bottom up when building the top of the root rib needs to be farther away from the tip than the lower edge of the root rib. To acheive this the rib guage needs to be inboard of the wing as the angle on the guage is about 91°.

A 2° offset angle will lift the wing tip spar by about 1" I will measure up latter and post what the angle should be for the dihedral, then when you press out your rib guage you can sand the correct angle into the appropriate edge.

What I have done is to set the wing onto the wing jigs and then to sand using a vertical sanding block.