has worked well for me in similar situations, clean real well and clamp 'til cured stuff is tuff.
If there is enough clearance on the outside of the frame.
Some would say rivet, but I would go with a couple of 1/8" stainless machine screws with flat and lock washers, that way you can tighten it should it loosen up.
Plus rivets may tend to loosen/shear over time.
"Sticks & stones can break your bones...and hail will dent your Airstream"
So when is this..."old enough to know better" supposed to kick in?