This might seem obvious to some, but I run into this on almost a daily basis at my shop-not that I don't need the work, but...
-Pickup Mounting Rings-
Some manufacturers include A ring with the pickup when you buy it-many times, it is more appropriate to plunder the screws & springs & toss it directly in a boneyard of spare parts, because the only thing that matters is the situation carved in wood -Body shape(carved or flat),neck angle relevant to the bridge, pickup position, and it's relationship to string height-in the axe on the slab before you.
-If you use single coils, then it's mainly the overall pickup height, & perhaps individual pole positions, if allowed by the design that you can use to tune the output signal by-
(we will not concern ourselves with guts in this tirade...pots,caps,jacks, etc. ...)
-But if you use Humbuckers,consider that you should be concerned with both coils being parallel to the strings to get all that bang you dropped yer bucks on.- Even in the simplest set up, say single bridge humbucker, single volume control, straight out the catflap, you are combining the signal of both coils to achieve the most powerful true HB sound-This is doubly true in a 4 wire harness, series/parallel switches , or shunted coils, phasing options...
-Point is, some rings are flat, some are slanted in profile, some are specific to arch tops, some to be bolted directly to the body way down in the hole...
The ring should suit the guitar body at the bottom, fitting snugly, and sealing off the gaping crevice around the pickup itself -blood, beer, and organic excretions will find their way in there anyway ,no matter what- in a short time, one could collect enough DNA to clone oneself, or perhaps be fingered for crimes, so clean that vacuum out !
Most pickups & rings use a two-screw mounting arrangement-this is fine enough, but means that your ring has to match yer axe!-you can adjust for height, but not the relative parallel of both coils- it may be neccesary to use foam, or a piece of wood to encourage the parallel, and then you have to fuss in your adjustments for height...mess with the size/shape of your "persuader" underneath,take the pickup in and out, etc.
-For the most part, once the pickup is installed properly and appropriate to the style of the wretch that will bash it to smithereens, one sets it, forgets it, and life goes on until something breaks, or changes...
-I like the 3-screw arrangement- Carvin uses this- with one screw on one side, and two on the other- this allows one to set the height, and the relative angle of both coils to the strings with considerably less muss...(& fuss)
Whatever the case, consider the axe, the parts included, and whatever else you have to buy,make,beg,borrow,or steal to do it right the first time, and get back to shredding...Cheers me bruthers!-Dracjavascript:emoticon('PDT_045')