Actually, In many cases, it's a good idea to over-form the ribs, say 87-85 deg as they "relax" on riveting.
Can't say specifically that I've seen this on a RV, but I've seen rib flanges "print" a line through the skin as a result of this "relaxation" after in-flight vibrations. I also put a slight roll on the edge so the contact point for the edge of the flange is a radius rather than an edge.
FWIW
mjb