Originally Posted by EastCoastCB
I don't think I'd weld there, as much as I do prefer welds when working with metal.
I'd drill into the ribs and use good fasteners. There are already hundreds of holes in the roof of a bus, what's a few more going to hurt if properly sealed?
Gotta break a few eggs sometimes.
I agree with this.
#14 self tapping screws with a 3/8 bolt head work great.
For reference, they are around the same size as a 1/4 bolts drilled through the outside flange of the ribs. There will already be rivets there, just drill a few out, clean the holes, and insert the bolts.
If the interior is out of the bus, I would use 1/4 inch bolts.