You really want the standard Gibson spacing for the humbucker poles. However the F-spaced ones are only 2mm wider in total pole spacing (the bobbins are the same size) so it wouldn't be the end of the world on the bridge pickup (if you look at Wazkelly's second EX picture it looks like the bridge could do with being slightly wider whilst the neck is pretty spot-on), and would probably look as much over-sized as a standard humbucker looks slightly undersized in that position. In the neck position one would look a bit out of place, but trembucker spacing is for bridge pickups only, so that shouldn't be an issue. Seymour Duncan say that if the string spacing between the two E strings at the centre of the bridge pickup position is 50mm or less, then use a normal humbucker. If it's greater, use a trembucker.