Re: hull extension in progress with pics
L77: PM sent w/ some suggestions and a few answers to your Questions...(PM = Private Message)
1: Start a thread for your Larson, oops will eventually respond to this post, but you'll get lots more traffic posting a thread in the Restoration section.
2: Read some more of oops thread & a few more, the PT question is well asked & answered in many places/threads. And a single layup of 4" tabbing up onto the hull is probably insufficient for either bonding to the existing (unless it's CSM) or strength (if it is CSM).
3: see step 1, if step 1 is fulfilled proceed to step 4
4: see 1st half of step 2, if step 2 is fulfilled proceed to step 5
5: Once you've read more then you ever thought you wanted or needed to know about fiberglass boats, their care & construction, repair &/or restoration, read at least that much again. It is never as simple as pulling the old deck & reinstalling new plywood & covering it w/ some fiberglass & resin. Especially when the boat has been subjected to waterlogged foam. <<--- This is more then likely going to cause both the transom & stringers to be compromised as well. Again see the 1st half of step 2, and proceed as indicated.
Welcome to dry dock & look forward to seeing you start a restoration thread for your Larson.