just had a quick butcher's at the dimarzio site and the outpupt difference is Paf Pro 300 and Fred 305 - would it make that much difference the other way round? i'm assuming if that is the case you'd have to tinker with all pickups in whatever position?The F-spaced does not make a HUGE difference, IMO, but it is a difference. Not as big a dfference as, say, different model pickups. I think the bigger issue is that the Fred is higher output (not by much, but higher) and you'd have to balance the pickup heights a bit to get a balance. You should give it a shot, though, and let us know how it turns out!