Phil,

The techniques described above are essentially the West System (Gougeon Bros.) recommended ways to secure fittings to foam core surfaces. Never use pop-rivets in such surfaces if you want to hold any kind of loading. A rivet requires very high compression against the rivet head and pulled section. This kind of compression cannot be achieved against cored composites and even just the laminate skin.

One tip I will add to the techniques described above...place the screws into the un-cured epoxy. Just spray them with WD-40 or cooking oil/PAM to allow them to release later on. This makes a very nice threaded section in the epoxy for maximum strength.

Mike.