I have already done the modifications but i cant figure what the string height (off the 12 fret) should be for 12-52 gauge strings.i have a ex50.ive been playin for 4 years and still cant figure out what the height is exactly.right now the height is 3mm off bass side and 2mm off of treble i think the action is to high and its harder to play but any lower and it starts to buzz.any ideas.the reason why is because i tune whole step down.
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Is your fretboard warped at all? if it is i'd adjust the truss rod, because i use 52's and my action isnt that incredibly high and theres no buzz.
Ted, just for future reference, a warped fretboard and an unadjusted truss rod are two completely different things.

Wormy: What I would advise you to do is adjust the truss rod so that the fretboard is completely straight. Then from there, slowly let some slack until the neck's bow is enough to let every fret play, but not enough to have to compensate with action.

If there is no possible way, then check to be sure your frets are level, and make sure that the fretboard is straight, no dips, twists, turns, loop-de-loops ect.
If you do have unlevel frets then take it to a shop, and get them leveled. If your fretboard doesn't appear straight (be aware there will be a slight bow in the neck to let hte strings play) when you look down at any angles, then you have a much bigger issue at hand.
Check the neck relief first(you should also make sure the nut height is set correctly too). I usually check an electric guitar by pressing down the low E string at the first fret and the 17th fret. I then measure the gap between the bottom of the string and the top of the 7-9th frets(many say just measure the 7th). You will have to capo the first fret or have someone help by holding down the string to make it easier while you measure with a feeler gauge. You want it to be +/- .010 inch. They say .005 to .015 is the range for neck relief. Mine are set up for .008 to .010 inch. You adjust the relief with the truss rod. Once you verify the neck relief is where you want it, you then set your string height. They say a good place is 3/64 on the high E and 4/64 on the low E. I've also heard, if it's 4/64, then it's probably set up well. Mine is set at 3/64 for both E strings, a hair lower on the high E, but not quite 2/64. After checking the above, if you still get string buzz at the string height that you want, then you probably need your frets to be filled level and recrowned, or, maybe you can get away with addressing the offending frets individually. I find it's better to go through all the work of leveling and recrowning the frets.