I agree on silicone, don't like it anywhere. EXCEPT on my Beckson ports. They are the only place I use it. If you think about the way they are built and installed, silicone makes sense, plus it works with their plastic. I removed, replaced and rebedded most of the eight of mine. I suggest you use silicone only for them. I am a great fan of butyl but it's hard to get it in the tiny space between the port protrusion and the outside layer of fiberglass.