Replying to Brakes need to be how much wider than ski width?

alright dudes, I already hooked myself up w/ some Salmon SPKs at 180cm which have a waist of 79mm. Salomon will hook me up w/ a wide selection of bindings, but I'm wondering to I need to go w/ the 80mm brake versions or the 85mm brake versions? I'm def going w/ the z10 ti series, though they may not be the quintessential freestyle break I'm getting them for NADA, so I just need to know if I need to give the greak a lil' room to breath, or go w/ the 80mm... gonna place the order here in a few mins.. so any help appreciated.. thanks...