My footman loops on 50 cal ammo cans and on my tubular DRE frame are about 20 years old now with no failures and no leaks. I used #10 or 12 machine screws with lockwashers inside the cans, neoprene flat washers and blue silicone on the outside. I tapped the holes in the frame for the same screws. Silicone on the outside of the can is more important than on the inside, but do both, just because you can.
Don't Wanna Die Askin' for Another Chance