My new arvs have an 11.5 inch tip rocker and a 10 inch tail rocker, which means if i mounted dead center, i would hav 1.5 more inches in snow contact behind my boot than in front of my boot, which would make the ski feel like i was mounted forward of center. If i mounted 3/4 of an inch back from dead center, or about 2 cm back (which is where the ski has a recommended mounting point) then the snow contacting camber area in front of the boot will be about equal to the camber length behind the boot.
spark notes: mounting dead center on an asymmetrically rockered ski is sheer autism.