Join Date: Jun 2016
Location: Orange County, CA
Coachwork: Crown, integral
Chassis: Crown Supercoach II (rear engine)
Engine: Detroit 6V92TAC, DDEC 2, Jake brake, Allison HT740
Rated Cap: 37,400 lbs GVWR
I would not trust self-tapping screws for anything more than a few pounds of load. I need to attach two steel angles to the ceiling for my kitchen's overhead cabinets, and because Crown used such hard steel that no self-tapping screw will cut a good thread into the roof ribs, and because the ribs are too thin for a machine thread, I instead bought a dozen Plus Nuts for the cabinets. They are like a Jack Nut on steroids, but much stronger than any Jack Nut (those have very weak threads and too-easily-deformable legs), and they will be more than sufficient to hold up my cabinets. They're not cheap, but peace of mind usually isn't. I also considered using Rivnuts, but again I doubt their ability to withstand high tensile loads, especially when I plan on dynamic loads of three times the static load for a moving vehicle.