T&T: Backing material

[Al Thomason]

Another school of thought:  Use NO sealant on the backing plates.  Idea is 
that if the topside caulking does fail (or more so, when it does fail) 
having sealed the bottom side will simply trap water in.  While leaving it 
'ala natural' will allow the water to flow through without causing potential 
larger issues, as well as give a good reminder that that fitting needs to be 
serviced :-)

If you have a cored deck (assuming your boat is Fiberglass) , make sure any 
penetration through the deck has had the core scraped out oversize, then 
filled back in with thickened epoxy and redrill the holes.  The West systems 
Fiberglass Boat Repair pamphlet has more on this.

-al-