G'day Hobie, what I discovered was that when one volume was turned all the way off no sound came out of the one left on 10 and vice versa.
Was playing the JB earlier today after cleaning it up from doing the DB Bone nut installation and yes Andy, it does make a big difference with no more dull or dead notes and plenty of ring or sustain on open notes. The action is a bit high at 1st fret and will work on that during the week.
Was also playing around with the volume knobs and by leaving both on 10 and backing one off slightly that is all you need to do to select which one is more in the mix rather than back it off a long way, hence why treble bleeds are not as important however I do recall some weird funky stuff that caused me to question that upgrade and decide to remove them both and probably in that build thread somewhere.
When stringing it up again today the damn D string tuner kept slipping and the cheap Chinese mystery metal feels like it is under fatigue and about to fail so later tonight or tomorrow I will order the $48 set from Real Parts. All up the only original hardware bits left will be the neck plate, scratch plate & control plate. Out of curiosity I will dig up all the receipts and add up how much it owes me. I am guessing about $500 including rectangular hard case but worth every cent.