Replying to Mounting AR6's/Will These Bindings Work?

hey newschoolers, I've got some ar6's being shipped in and I had a few questions on getting them
mounted. where should I mount them at? center? or -2.5 cm? it seems like it goes back and forth when I search for which is best. I'd like to be able to ski switch comfortably and what not.
I got a pair of binding for free from a friend, they are rossignol axial 140s. right now they are on a pair of old skis but I'll be using them. will these be fine for skiing park? also they have a base plate on them right now, but is it alright to use them without the plate? I don't see many park skiers using base plate with their bindings. lastly, should I take them off myself to get them mounted or should I just bring in the old skis with the bindings still attached and just tell them that I don't want the base plate put on the new skis?
thanks guys!