After building my Arctic Tern, I paid more attention to the technique used in other boats, especially the local Michigan-made Betsie Bay plywood kayaks. I was suprised at the size of the fillets that are generally used. The ones I put in my Pygmy measure only about 1/2" across, so there's still a fairly sharp transition as you go from panel to panel. But the Betsie Bays use very large fillets, measuring more like 1 1/2" across. There's a lot of epoxy there, but their boats are still very light-weight. I'm not sure what kind of fillers (wood flour, Cab-O-Sil, etc.) they use.

Dean