whats the difference between an F-Space pickup and a regular
One Google search and I found this on the Dimarzio site:
"F-SPACING refers to a wider spacing between pole pieces available at no extra charge on all full-sized humbuckers. F-spaced pickups should be used in the bridge position an all guitars with wider string spacing, such as STRATŪs or guitars with tremolos. This assures proper string alignment and balanced output. On guitars with a nut width of 1&11/16" or greater, F-spaced pickups can used in the neck position as well. Please specify "F-spaced" at the time you place your order."
BTW, Ibanez RG guitars have a neck width of 43mm (~ 1 & 11/16) so I use F-spaced in the bridge AND neck positions.