Gougeon West System Epoxy definetly sticks adequately to the Beckson portal rings in this application. The portal with the lid in it is very strong. Without the lid of course the portal is not very strong. Overall portals improve the boat and will add to the life and strength of the hull.

I would strongly recommend against silicon or any soft adhesives. Only something like epoxy will put the portal in in a manner that is not detrimental to the strength of the boat.

I have added portals in this fashion to 2 Nacra 6.0s and 1 Hobie 16. On the Hobie 16 I did it as part of a project to epoxy the whole boat together. As part of the project I was weighing the boat by component. Each Hobie 16 hull lost approx. 5 lbs in the first 24 hours of having the hull openned up to good air circulation. And each hull lost a total of between 8 and 9 lbs over a weeks time. The negative effect of the moisture in the hull, saturating the fiberglass, will outweigh any disadvantages of a portal, preferably two per hull (The 6.0 is lucky to already have one by the rear beam). The effect is only increased if you live in a northern clime and your boat is exposed to freezing and thawing.