Ditch the POR15. I have a fiberglass tanked and it failed not once, but twice.
I'd used Caswell sealant. Put that in over a year ago for my fiberglass tank and not one single problem since. Much better product from both a chemical and user standpoint. Best $60 I've spent.
"Living just to keep going, goin' just to be sane." - The Black Keys
I prefer kick starters, air-cooling, and carburetors over anything.