Re: fiberglass, gelcoat, floor???
Is it just the floor, or the hull bottom itself?
Eatherway, just forget about the gel coat unless your planing to make a mold and completely remake the lower hull.
simple way to do it, is (using a single direction high-speed saw, so NOT a sawzall) cut out more than the damaged area. lay down wood, and fiberglass over that.
then sand, paint, and enjoy
Ill be doing this also in the next few days and can supply pic if nessary.