I have a couple of boards that I got while traveling in New Zealand that have single fin boxes with edges that are keyed in a dovetail pattern. It’s a pretty good idea, it seems it would add a little extra strength to the fin box area. I haven’t seen any boxes like that available over here, though. Has anyone seen boxes like this, or does anyone know where to get them?
Yes… I believe they are called “chinook” boxes for wind surfing. Regular fins fit them. The bond of resin/glass to the box is excellent… I’ve repaired them at the front - fin impact still causes cracks where the resin/glass meet the foam/stringer. The resin/glass appeared to still be firmly bonded at the box though.