How low do you guys run your humbuckers on a semihollow body? i friend of mine who has mre experiance says mine was to high and lowered it almost flush with outer plastic peice they are non covered. i have a Dot Studio.
It depends on the pickups, and string height. Most of the time, you want it close enough to get the most output out of the pickup. But you don't want it so close that that the magnets in the pickup actually draw the strings towards it. Just play around with the height till you find what you like.
PRS SE Custom 24
Jackson DKA7
Gibson Explorer
MESA/Boogie Express 5:25

Dunlop Cry Baby Classic
VOX Joe Satriani Ice 9 OD Pedal
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Ernie Ball Strings
V Picks
i have it till i likie the sound of it(if the guitar has seperate volume knowbs)
if moster volume i try to balance best sound to even output
To measure the string height do i measure from the part of the pup that has the slot for a srewdriver tip?(is this the magnet pole?) i know to measure from bottom of string fretted on highest fret.just not sure of the other part.
There are no rules about how high your pickups should be. Closer to the strings will make the tone sharper and it'll give you more volume. Further from the strings has a more open tone and less output.

If your pickup is too close to the strings then you might get feedback problems or the string might end up touching the pickup when you fret the higher notes so it's important to make sure your strings clear the pickup even when you play the highest fret.

Aside from that you just do what sounds good to you.
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