I think your best bet would be to contact Catalina directly for the structural information - you'll get the best info that way (have your HIN number ready) By all accounts they are very helpful.
Beyond that I think you'll at least be doing some exploratory grinding sometime soon!
1984 Fast/Nicholson 345 "FastForward"
".. there is much you could do at sea with common sense.. and very little you could do without it.."
Capt G E Ericson (from "The Cruel Sea" by Nicholas Monsarrat)