Can you modify the fitting so that it doesn't contact the deck at all anymore? Seems odd that the clearance is that tight for such a fitting.. As a deck stepped mast there really shouldn't be anything other than the mast tube contacting the deck area.
Photos would help...
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)