Re: F Spacing, what is it exactly???
F spaced pick ups (called Trembuckers by Duncan) are just normal pick ups. The only real difference is that with tremelo bridges the strings are a little further apart, so the the polepieces are also further apart on F spaced pick ups. F stands for Fender since they started building tremelo bridges or something. Putting a normal humbucker in a tremelo equipped axe, isn't really bad for your tone or anything, the difference in sound is hardly noticible although some people claim they do notice difference in sound. Visa versa with putting F spaced pick ups in hardtail guitars. You do have some tune-o-matic or hardtail bridges with F spacing, but I believe you also have some tremelo bridges with regular spacing. The F spacing also only applied for the bridge position, real neck humbuckers don't have F-Spacing.
We had a topic a little while ago about the F Spaced pick ups sounding a little bassier because Floyd guitars make the bridge position sound thin. I don't know if it's just a rumour, but it might very well be true (I've got a rather dark sounding TB-4 JB in my axe as well). I hope somebody can comment on that further
Hope I answered your question