/I've seen extenders, but how does one get the tap securing back nuts to do their job when the same bit of thread they would use is now taken by the extender?? Grrr /q

Slightly more awake....

The thing with extenders that's got me stumped is if there's only a few mm of tap tail showing under the worktop, how do you get a good seal ? I'd expect that ideally they should be done up tight and seal on the flat faces of the tap tails, but without frigging about with the worktop that's not going to be possible... what are my chances of getting a seal just on the few threads showing? And with what? Ptfe?

Cheers
Jim K