I used POR15 in my race tank, supposed to be methanol proof, but most has quietly peeled off which has been a pain. (clogged filters)
Personally I'm now erring more towards the addition of upper cylinder lube or 2 stroke not just helping the engine but also protecting the tank.
As for my race tank, it still has remnant POR treatment (adding no value) and is sloshed around with oils once the methanol is drained.
I haven't tried to remove the remnant POR. I guess soaking with acetone would be the answer.