The other day, I came across a video on YouTube of a John Mayall & the Bluesbreakers performance back when Walter Trout and Coco Montoya were the dual guitarists. Montoya was playing a Strat with 3 of the "rail" style pickups in it. Personally, I didn't like the tone as much as the vintage single coil Strat sound, but it'll give you something to watch/listen to and hear what a 3-rail p'up setup sounds like. I don't have the link handy, but do a search on "Bluesbreakers", and I'm sure you'll find it.

BTW, Montoya certainly has a unique setup. He's a lefty, and he's playing a left-handed Strat, but it's strung upside down, i.e. like a RH Strat. Apparently, he learned on a normally strung RH Strat and he prefers the "big strings down", but he wants the deeper cutaway on the correct side!