Thanks for the replies!
Tsunamichuck, did you have a link or photo for your setup?
My main concern is not harming the hull or frame members. I suppose I should start taking more care for my back, too, but I've been shoving my 40-ish pound Wisper and Kahuna on top of a camper shell for a dozen years now.
Just now, I opened up Ralph Diaz' book and looked up cartopping, and he doesn't really warn against racks; rather, he recommends nylon-coated foam like windsurfer rack pads. Sounds like that's what gbellware is using.
Not sure where I got the idea that you shouldn't use racks with a folder . . . but the foam flat-on-roof cradles with ropes protected with pipe insulation have worked like a charm over the years.
Change is so hard