Did approx. three hours.
I finally plucked up the courage to put grinder to fiberglass. If you are unsure what I mean.... take 'glass' fibers, toxic plastic resins and put a grinder wheel to it that sends the microscopic particles and nasty fumes EVERYWHERE!
Full body dust suit, goggles, respirator, ear protection, dust extractor and I still got the stuff all through me (can you say "prickly skin")!
At least I got the front bow support out and all the rough edges ground down. Hopefully it's the first and last time I have to get up into the bow of the boat with the grinder.