Hey brotherbd, here's what I did.
A drum with a crimped seal, not rolled. This is an open top drum, so used the bottom for this part.
Cut 3/4" below the first bulge.
Beat the heck out of the bulge to expand it a bit. I used a 3# hammer and an anvil.
A close up.
And sitting on the drum.
This was done to accept a Weber top and a rotisserie unit, but will certainly work as high top cover for your drums. It will need an exhaust of some sort though.
Have fun with the project and I hope this was of some help to you.