Not the best picture and I have yet to find out of the minor imperfections are going to be an issue but I tried this
Cut some 2x4s on a band saw to fit the curve. The ceiling studs are about 1/4 in lower than the metal ribs. Pl premium and self tappers. Wasn't sure what I was going to put on the ribs for that 1/4 inch but someone mentioned something up there I may look into. Or spray foam on them and try to cut it flush. Anyways it seemed to make sense to me.