Hi Michael
I'm not familiar with the CH750 geometry but I would guess that the sheet metal skin that you are looking for is curved in one direction ONLY, and therefore you can reproduce the skin in SW using a lofted surface (or solid) between two (only two) profiles represented by the ribs and spars. I'm assuming that the spar segments between the ribs are straight lines - otherwise the skin has multiple curvature directions - a completely different kettle of fish.
Hope I understood your problem correctly.
Jeffrey