Just did the end pours on my SW Hybrid sport. I used West Epoxy, with 1/2 fast hardener, and 1/2 slow hardener, with light weight filler. I left is very viscous, and poured it in the bow. It appeared to be kicking off, so I left for awhile. When I came back, it had expanded to at least double the original volume. It looked like expandable foam. I was able to break off the piece that expanded way out, so it is about 7" deep. I mixed just epoxy, and poured it in to fill around where it had pulled away.
The second pour, I used wood flour, and left it even thinner. That expanded about 50% above what was poured in. I left it as it is. My concern now is that the pours appear to be very pourous, just like expanded pour in foam. When I drill for the handle toggles, I will super saturate the complete hole from one side to another, so it doesn't absorb water.
I have never seen epoxy expand like that, it really looks like foam. I will probably send an inquirey to West and see if they can tell me what went wrong. It won't be a big problem, but I am real curious why it happened.