I've recently discovered the joys of Gflex and am now a believer. It bonds to everything and is flexible enough to be tough and not brittle. I just had to reattach a fiberglass
sheet to my polyethylene holding tank
and Gflex did it beautifully. Polyethylene is really hard to bond to. I also just bonded some stainless steel
with it and it bonded so well that I could not lift
an edge with a screwdriver trying my best. It it just that tenacious.
If it was my tank, I would clean, dry and prep the surface, throw some Gflex on it, and know it would be good to go. Super easy.
I also agree with the post that says don't worry about it, but then again, any leak of any size can just drive a sailor crazy. It's sort of the broken window effect. Let a small leak go, and then...
Good luck on the refit