Fiberglass work

[Blue_Runner]

use a angle grinder and grind all mating edges at an angle also grind off all gel coat or paint as much as six inches if you can exposing the fresh resin or mat

These guys will tell you I'm not in the glass business....but I had a '73 V20 transom replaced by a glass shop once. He went from the back just as you did but instead of cutting, he ground it down with the grinder all the way through to remove the skin. Similar to wht Nymack is referring to.

I went to the shop just after he took off the skin and he was solid white with glass and gelcoat dust. I'll just stick to boating/fishing.