Replying to Sizing for rockered skis

So I work at a shop at Bachelor and have been wondering what people think about how to size people for rockered skis.  The thought that we have been having is since most double rockered skis ski so much shorter due less actual surface contact that we have giving people a size longer than they might normally ride.  Example I've put people on 179 (actually they are 182 but whatever) obsethed's that would normally ride something 10 cm shorter even for powder.

Thoughts?