Using drawing 6a, I located the rib location. I found that using cleaco clamps and .032 shims to simulate the skin when clamping will "auto center" the rib. Works great! also helps you identify areas where the skin is not going to bridge flat between the rib flange and the spar.
I use blocks gluded to the table to hold it all in the correct position. (forgot to take a picture!)
