You can balance out the levels of individual strings with the adjustable pole pieces though I've never found it to be necessary.
Yeah, I'm pretty sure that was the whole idea behind having adjustable pole pieces in the first place. But, like you, I have never found much balancing adjustment necessary. I guess it was more of a problem back in that days of heavy flatwounds, because you'd see a lot of pickups with the polepiece under the B string greatly reduced or backed off - even occasionally eliminated.
Ah, there ya go!
You can also make the pickup sound brighter (to my ears) by lowering the pickup and raising the pole pieces.
I have LONG thought that by adjusting ALL the polepieces to an exagerated height - in OR out - you could "unbalance" the two coils of the humbucker - meaning, the two coils will have slightly different output. It's been postulated that some of the PAF tone-mojo was caused by the imprecision of the coil-winding operation, resulting in unbalanced/unequal output coils. It's never what the adjustable polepiece was intended for, but I think that it works.
FWIW, I do this ("unbalancing") to every neck
pup of every humbuckered guitar I own.
Not really off-topic, but wandering around it a bit...
MORE: I have been lowering the pickup and raising the pole pieces for years, but recently a re-think had me try raising the neck pickup and lowering the polepieces, and I seem to be getting the same affect. The reason for the change in plan was to see how this scheme of adjustments might work:
I always turn the bridge pup around so that the slug coils are closest to the bridge, the screw coils closer to the neck pup (I have done this for years). I do this because when I do coil-shunts, I like to keep the screw coil active, so that I can have some adjustment, and putting the screw coils farther from the bridge puts them where they might be getting more kinetic energy - the string describes a wider arc.
It's why bridge pups are usually wound hotter than neck pups, to "balance" properly - the farther from the bridge, the more kinetic energy, louder the pickup will be.
By raising the polepiece screws in the bridge pup AND rotating it, I think I can get a louder single coil sound out of it - so the coil-shunt tone isn't such a big drop off in volume as it might be.
NEW: for the neck pup, leave the slug coil active (instead of my usual screw-coil idea). Now, when I have the pups in coil-shunt and play them together, I still have a noise-canceling pair of coils playing. This is something new for me, but I think PRS has done this with their humbuckers from the get-go (coil-shunt leaves a noise-canceling pair). So on my neck pup, with the slug-coil active, I'm LOWERING the screws down into the pickup to make the slug-coil the hotter of the two, again, to unbalance the coils and make the change from humbucker to coil-shunt less of a drop in gain.
BECAUSE I have turned the bridge pup around, the two coils playing in shunt are the two closest together, giving me the best "quack" - just as the old-school coil-shunt setup of shunting to ground has always given you the "inside" coils - IF you didn't rotate the bridge pup as I do. So, this is new for me.
So now when I go to coil-shunt: I've got a noise canceling pair; it plays the two coils closest together; and the the coils playing are the louder of the two (unbalanced) coils of each humbucker. Whoohoo!
I JUST did these adjustments to my LP Special, and in the music room it sounds pretty good - I must say, I'm amazed at how much better the gain/volume balances between the coil-shunt and full humbucker tones.
Could just be the "new toy" syndrome, but I really like it... and I'd like to give you a solid thumbs-up stage report, but I ain't gigging anymore, so this axe probably won't see a stage until our annual reunion jam next spring. But the results of my testing so far have been encouraging enough that I'm probably going to make this change to my ES-333 and faded V, soon.
So, I'd love to hear from someone else who wants to try this. If you already have coil-shunts in your axe, it's really a pretty simple collection of ideas: change the shunt lead for ONE of your pups, rotate the bridge pup, adjust the polepieces as indicated...