Hi Ed, I'm in complete agreement with you with the health and environmental issues of polyester and vinylester resins. The problem of laying up an expoxy laminate over a polyester one is two fold. Firstly,its very hard to achieve a good bond as expoxy doesn't adhere well to polyester and secondly, polyester is a very unstable material and is prone to shrinkage and warpage. Epoxy on the other hand is quite stable, especially the higher quality ones. When you mix the two systems you will end up with the polyester shrinking around the epoxy patch and that will show on the fuselage surface at the very least. It will probably lead to delamination over time too.Regards,Ian