I have used Pettit for many years on boats big and small. My most recent experience has been with Hydrocoat SR. My fathers 18 Parker had made it over 20 years without bottom paint and looked showroom new. Much to my dismay he had finally reached a point where he just wasn't wanting to continue to have the maintenance associated with a boat that had no bottom paint.
I suggested barrier coat and the HydroCoat SR. He had the yard down at his summer place do the prep and application. After putting the boat in the water for 2 days the paint was coming off from the chine to the waterline which prompted him to pull the boat and inspect the rest. He sent me pictures and I immediately knew the issue. The paint crew had waited too long after applying the barrier coat to the apply the HydroCoat SR. No bond had occurred either chemically or mechanically between the barrier coat and the HydroCoat SR.
He had the yard contact me and I asked vague questions and just as I suspected too much time had passed. " We applied the barrier coat at noon and let it dry overnight before putting on the bottom paint" The yard attempted to tell me it wasn't there fault and not their problem since he had supplied the products. I made a deal with the yard that if I sanded off the bottom paint, prepped and applied the Hydrocoat SR from the same cans he supplied and it stuck that they would eat the bill for the application labor and materials. You know how this turned out!
IT STUCK !
Prep and proper application is the key to any paint product. I suspect the issue in your case is hot with the product but with the application.