Shouldn't I use the hex impression copings for open tray impression for a bridge?

Shouldn't I use the hex impression copings for open tray impression for a bridge? If I use them, shouldn't I splint them together with GC resin pattern? I did it once recently (as the supplier does not have non-hex impression copings), it was VERY hard to take the PVS impression out of the mouth. I also heard a cracking sound of the pattern resin inside the impression.