Sorry - It's the X series that has 1 less bearing between the Chromo and the Stainless model.

As for cadence magnet on the end of the axle. I have used a magnet on the end of my pedal spindles for years and I know I used them with stainless Zero pedals. Don't know how well they stuck but yes - in general many Stainless alloys are non-magnetic (how we tell stainless in auctions when looking for scrap - huge scrap value difference), but it is a moot point. Take a tube of clear silicone outside caulk and fill the end of the axle, put the magnet on and then wipe away the excess. Works like a charm and has served me well for years.