... below the waterline and for things like fuel fills (butyl is not fuel-resistant).

Agreed that butyl is good stuff where you can use it, which is most places. I have some old rolls that are lord-knows-how-old (very dusty from back of stock room and had "historical era" price sticker on them). They still stretch like crazy (major elongation without tearing), whereas some other stuff I got new from a "good" source breaks within a few inches (not Maine Sail product; sounds like his is like my older stuff and I plan to order some from him soon because I'm running out of the old stash).

I'm trying to decide what to use on fuel fills and near-waterline through hulls now - I've gotten very spoiled with butyl (although the caulk tube version is not nearly as user-friendly as the tape!).

CCA-Boater