I have some 306mm boots currently, but the pair that seems to fit me the best for my new set is 300 flat. Do FKS's have the adjustability of atleast 6mm so I don't need a remount?
You should be good with less than 10mm difference, you just have to adjust the screws on top of the arms and make sure the forward pressure indicator is level with the two black raised marks and if it is, you're good.