Funny how sillycone is considered the bane of all marine sealants and Dow 795 is suggested for deadlight mounting in AL frames. 795 is a silicone sealant! I used it anyway. Can't leak any worse than before if it doesn't hold for a year.
Chas - Silicone is kind of a generic name for a family of sealants and adhesives. They are not created equal! The product sold as Marine Silicone is not the same as bathroom silicone and definitely not same as Dow's 795 which is a structural adhesive.
795 adheres to acrylic and other plastics as well as to aluminum and glass. Marine silicone does not. Don't worry about your 795 not lasting long. My ports have been in for 3 or 4 years and still are 100% good. So much better than those crappy rubber splines so many boat ports have.