Totally agree with Monitor, I use #5 ykk all the time on my jacket since at my size 36 anything bigger looks out of scale, the local jacket maker I go to, which would grant whatever whimsical ideas I throw at them, only ever refuse to do one thing. burying the zipper tape like aero does. its like stepping on brake pedal while giving gas every time you operate the zipper.Occasionally, the pull-tab or worst case scenario, the entire front of the zipper machine will break off clean, too.
I strongly believe that the main cause for zipper failure on Aero's main line jackets is 'cause they're burying them so deeply. Zipper tape must have some give in order to allow the teeth to align naturally which, held firmly in place by massively stiff, thick leather, becomes nearly impossible. Proof for this is that I don't ever recall reading about the same type of zipper breaking down on any of Aero's A-2 jackets, as they have fully exposed zipper tape.