For the poster, around -2.5 sounds perfect, if I understand correctly then you're not exactly all about park, and like to ski elsewhere too. Hence a little further back will be fine. If anyone says a centermount won't affect your all mountain skiing then they're wrong. Thats a fact. And keep in mind, 2.5 cm really isn't all that much. Having them back a little will not really affect your park skiing much.
I say go -2.5.