So... got the tank back. Chris Cruz did a great job on it. I decided to scrap the paint saver just so that I can keep an eye on the edge... Chris told me that if I see any kind of bubbling on the edge, then he can fix it easily (and cheaply) as opposed to if the ring is on there and I don't see the issue until it is an inch or so into the paint. He added an epoxy ring around the paint line to help bolster the edge.
So, I went with a harley style cap... all aluminum and vented at the center. This is a joker machine piece... seems to vent well.