Hmmm.......I have shot the heck out of mine with no problems. They stick just fine, in fact, I can't pull them off if I try.
The only difference I can think of is you are using aluminum. Come to think of it, I don't think any of us who have done the spray cresting have used anything but carbon. I wouldn't think that would make any difference, but it's the only difference I can think of.
I have some old aluminum lying around, give me some time to get some done, and I'll see what I can come up with.