Just to separate my thoughts a bit here, I got some polyurethane paint at a swap meet in Florida, Ferrari yellow, to paint my planes with. The sales guy whom I wanted to somewhat believe, said the generic hardeners would work on the urethane, as well as the regular acrylic enamels that they are made for. I hope he is right. On some other thread, maybe here somewhere, or RCG, the "industrial or commercial?" Tremclad, or some other large commercial brand was supposed to have worked well with the automotive hardener. Another thing I would like to believe. I tested a two part epoxy water based floor paint on a flutterboard to make into an airboat. It is kind of heavy, but seems to be very fuelproof. Grey or a tan colour kind of sucks.