I've seen some major resto projects in progress at a shop last week. I was shown 2 big powerboats. A 38' go fast boat and a 30' Fishing boat.
They cut the aft end of the fishing boat right off about 3'-4' forward into the boat. They totally put back a new one on that they made and 2 huge outboards were hung on it. You would never know. Looks perfect.
The go fast boat had the whole bottom delam at high speed and sunk in California. These guys bought the salvage and toally reworked the transom and put a brand new bottom on her with with fiberglass mat, fiberglass cloth, resin, filler, gelcoat, and hard work. Looks brand new.
It's amazing what you can do with fiberglass.
I am doing some small hole repair on a Hobie 16 that I own. One's around softball sized. Then a couple of golfball sized holes as well. Very easy so far. They say the hard part is the prep. So I have that part all done. I start laying glass very soon. Hopefully next week.
I found a site called US Composites. They have very inexpensive resins, fillers, and gelcoat. Try them at: Fiberglass , Composites, Carbon Fiber - U.S. Composites, Inc.
. You can find great deals on fiberglass cloth on ebay. Search: "fiberglass cloth"
I'm telling everyone I know doing fiberglass repair about these guys. I have no idea if you are considering doing it yourself or not but you never know. Hope this helps.