I am also going to try a hand layup with a different epoxy i use for hand lays along side my resin research 2050 and make two small 15"x 15" test panels. It is thicker so not ideal for infusion, but has been my go to since i started making carbon parts a few years ago. I will give that resin a try and see if it does a better job bonding to the GC50. I have had a cheap epoxy off of ebay not mechanically bond to anything before, so i know that the type of epoxy can be an issue. So trying my go to epoxy that i know bonds to everything next to my infusion epoxy will prove real quick if its an epoxy issue. I have used this epoxy as a depth coat on a million things and never had it not bond to what ever i laid it over. So if that test panel does not bond, i am going to be very confused. Lucky for me, if the epoxy proves to be the issue i can get away with hand lays for a while due to using a gel coat and not having to worry about pin holes until i find a compatible infusion epoxy here in the states.