Just installed a new radiator and valves for mother-in-law, had to cut and shut some pipe but all good... except the damn tails on the radiator (where they connection into the actual radiator) are leaking. I've taken them apart again, cleaned up, plenty of ptfe and screwed back in, and still dripping. I cant physically do them any tighter into the radiator, so at a loss as to what to do now? Thinking of trying boss white or something? Words of wisdom welcome, as never had anything like this happen before.