Ed and Robert, yes I was talking about the difference between the blue board and the jet fighter/yacht foam. The blue board is not as closed cell as one would hope, and it has little compression strength when compared to diviny cell. Ed, I've read that same research and I would have no problem with using the foam used in the research except that I don't want a second mortgage on my house to build a dingy- there are much cheaper ways as you know.
I think the hot air delamination is caused by the multiple layers of 2 inch foam board creating large air pockets between them. On the 'fuge, I think two other foam builders mentioned this last summer as problems with their boats. In all a small population of builders, and only 3 mention this as an issue. I know that on my boat I had gaps between the wide faces of the sheets that I couldn't fill with expanding foam once things were cured.
As hard as hunters use their gear it is important that they have something that they can bash up a bit and not worry about it. A foam boat will have a hard time in this environment, unless it is loved and coddled.
However, it is really hard for the home builder to make a boat with curved chines if they can't mill cedar strips. With foam you can make a well rounded hull with some rocker all by using sand paper and a day in the driveway. But you will have to care for the boat more than any other piece of gear.
Last winter I played with some 1" blue board and a frame to hold the foam in compression so that it would have the cross section of a KARA. I placed a layer of 4oz glass on each side using RAKA. This test piece of foam hull turned out shockingly strong in its arched shape. It gave me hope for my next foam boat, but I could not get the build method to work out since the 1" blue board would only bend so far, and could not bend in a compound curve at that thickness without breaking. If it was thinner it would have worked, but we don't get 1/2" blue board here. We can get 1/2" diviny cell though and it won't take that much of it, so maybe one day.
Right now I am thinking of cedar strip mini sneakboxes just because the materials are dirt cheap and the smell when milling it just too nice.