When I did my tanks, I had some of that blue/gray vinyl stuff that they put under bathtubs.
I glued a strip on the tank with contact cement.
The good stuff with all the fire warning labels.
Then, I glued a strip on the strap, and put some grease between the two when I strapped it down.
Thats the way I do my across the bed toolboxes. Two strips, one glued to the truck bed, one glued to the toolbox. Grease in-between.
Unless you weld them, there will always be a slight amount of movement, and I want the movement to be between the strips, with minimum wear.