A sheet of 3/4" Starboard will fix most of what you want.
The hatch is a prize to find though.
If you ain't already seen it, look through this thread. Might give you some ideas.
http://www.wellcraftv20.com/communit...ighlight=specs
Some of the Starboard stuff starts on page 14.
Hatch repairs (if you had the hatch).
http://www.wellcraftv20.com/communit...hlight=correct