stewart, I feel your pain, I fear that even if you spend the money for system 6, you wont be happy. I can't tell you how many times I thought about a similar repair. It only took one attempt of applying system 6 to realize that the job best be left to pros. The whole idea of a MEK and PVC mix is a nightmare waiting to happen.
With that said, Cascaide outfitters had the best deal on urethane that I have seen in a while. Good Luck
Gallon Urethane Kit | Cascade Outfitters