love to hear some reports from those who own one of these beauties...I'd be especially interested in knowing how people get on with the middle pickup...I was convinced I wanted a 509 until I played one and found my picking style completely incompatible with the height of the middle pup - the Special with its narrow filed looks lower profile but curious was owners say...
The Middle on a Special is only ever active with either the Neck or Bridge - you can't actually play 'just' the Narrowfield on its own - at least not without modding. The Special is a 'Custom 22-08' essentially so in the 'middle' position, you get both Neck & Bridge. Positions 2 and 4 engage the NF but only with the Neck or Bridge pick up. That difference gives the Special 12 different selection options compared to the 9 in the 509 because position 3 has 4options (Bridge & Neck in either HB or SC so HH, HS, SH or SS) on the Special and just the 1 option - the middle 'Single Coil' on the 509.
The 'middle' pick up on the Special is great but like I said, on a stock Special, you only get to hear it in combination with either the Bridge or Neck pickup. You can do the 'Position' 4 on a Strat type combo with a Split Neck and NF for example.
As for the middle pick up in the way, I would imagine you'd have similar issues - maybe more as the NF's are stepped compared to the more 'smoother' profile of the 509 pups. Like everything though, I recommend trying one if you can as it might not be in the way of your playing style or you might be able to lower it a bit...