The big-assed allen bolts on the Seymour Duncan SH-8 Invader are used to give the pole-pieces more surface area and a unique voicing.
Compare the Invader to the Dimebucker (which uses rails) to hear what I'm on about, as they're identical, aside from the poles.
Not quite the answer you're looking for, I'm sure, but I figured I would chime in, regardless.