Fastener ?

[billiebob]

10 years later, aluminium over steel tubing with self tapping screws is unbeatable. A 5x10 cargo trailer for $2900.

And so easy to modify. You cannot do that with welding, glue, composites, epoxies.
Less than $200 and an afternoon added the left side door.

 

[ajmaudio]

Its been said a bunch but VHB or perhaps one of the Sika adhesives like 252, if memory serves, would work great. 3m is actually great to deal with, as mentioned you can get an engineer on the phone easily that will direct you to the appropriate product. They even have VHB that can survive a powder coating oven....