I had Navman instruments installed in the holes left by my old
Datamarine instruments. The yard that installed them glued a backing
board inside the bulkhead where the old holes were and drilled a 2
inch hole in the backing board. The Navman instrument face covers the
old hole completely on the outside and I was able to use the backing
board because the inside of the bulkhead where the instruments are
mounted are inside a cabinet, so that side does not show. If the
instruments are mounted where you can see the back side of them, a
nice teak board inside w/2" holes might suffce.