Re: Hot Rails -> Pickup height
The Rails configuration produces a closer magnetic field. Since the magnetic field flows from the one blade to the other, and they are very close to eachother, it is a low field. (not low in power, low in shape)
So if you think of a Strat's magnetic field like a water fountain squirting straight up and out, a Rails pickup is more like attaching a short hose from one blade to the other.
This means that if you get it really close, it will be a lot louder, and once you get it farther than say...1/8" it will lose output. But they're hot pickups anyway so you can surely back them away from the strings with good results, I'm just saying they're more sensitive to pickup height than traditional single coils.