Thanks, Vladan.
Whilst I'd like to do a thorough job on this attenuator, I really need to clear my bench. This whole thing has gone on far too long and I have a backlog of 'stuff' to deal with. Consequently, I'm going to have to put it back together as-is and deal with the o-rings as and when they fail in the future, much as I'd like to sort them out now. It's unfortunate, but time just isn't on my side.
Jinxie