Sorry I didn't get back to you sooner off-line. Yeah, they're surfboard guys. Fiberglassing is fiberglassing though. I tried the KK a few times on the Night Heron. It IS faster than the Fast hardener and that's about it. Both are quite viscous, though. I found it was easier to laminate the cloth using MAS and then use the RR for fill coats. The fast also UV protection so it can be used as the final coat on the interior. If you use their sanding agent called Additive F be warned: Use it only on the final coat. It has wax in it. You WILL have to sand it in order to get anything to stick to it.... even if the base coat is still green.