Paul, Very happy with the fitting.
I used the RA140 shown on the following link.
Glomex - The best in Marine Antennas - GAMMA PRODOTTI
I drilled a pilot hole followed by a larger drill for the center cable hole.
I filled the RA140 with Lexal to seal it. I then drilled 3 pilot holes for stainless screws, filled the holes with more Lexal and screwed the into a Lexal bath, wiping it clean afterward.
I had 2-40 watt panels. If I were doing it over I would use a single panel. Incased the panel wires in split corrogated cable cover available at Walmarts.