I remember that the foam up under the side decks (gunwales) of my 1969 Widgeon was jammed in there pretty tight. I'm not sure if there really was any kind of glue, other than maybe a foam-in-place type urethane foam? I know that is how the foam is attached to the underside of the deck in my 1979 DS II.
I looked at a Widgeon at D&R Marine last Spring that was more of a "kit", a previous owner had taken the boat apart to restore but gave up and traded the old boat for a new one that Rudy had. I might have bought the old boat as a project, but being out of work....... $200 was pretty hard to come by. Anyway..... the foam was ALL gone on that boat and I got to thinking just how would I have replaced it? My though was to put the boat up on saw horses upside down and pour some foam-in-place urethane foam into the gunwales, I'd have to block off the area around any fittings to allow access for bolting them to the deck.... but I figure it would have worked. Polystyrene foam cut to shape and set in expanding foam might also work, or maybe Gorilla Glue?
As far as the foam inside the mast....... I'm not sure I'd worry about that. I suspect it isn't really needed unless you happened to drop the mast in deep water. It might have a very, very small effect on preventing the boat from turtling..... but I can't imagine it really having much effect. I never tipped over in the 7 years that I sailed my Widgeon, but the boat did fill with water and roll over at the mooring in a storm, by the time that I came down to bail her out, my neighbor had already righted her for me. I think he said that she was all the way over... ie: mast had gone underwater, so... the foam doesn't do much.
I suspect that one of those "blimps" like HOBIE offered to mount at the masthead would do more to CAUSE a capsize on a Widgeon than anything else (too much weight aloft). Maybe an inflatable life jacket could be rigged up on masthead? O'Day did offer something like that back in the early 1970s <GRIN!> It was a balloon that would inflate if the boat capsized, problem was that it only worked once!
O'Day's description:
Masthead Flotation Device.
Here's a light weight, positive-acting flotation bubble that's actuated by immersion. Even the best-designed boat can "turn turtle" under extreme conditions. In the event of a capsize, a rubber balloon fills with CO2 to help keep mast at water level