Hi Longhorn, I am a long way from being an authority on POR 15 but I have an opinion on what went wrong. POR 15 reacts with iron oxide to create new chemistry that is important to how well it "sticks" to the metal. If you had the frame sand blasted there was more than likely no rust left for the POR 15 to react to. I am not sure having the frame sand blasted and then using POR15 was the right thing to do. I think you would have been better off using a good quality primer and paint after the sand blasting. Not what you wanted to hear, but better to figure it out now when the body is still off.
Rick
