On demo bindings like the Marker Griffon Demo and the Salmon Z12 Demo, are you able to change or move the boot center forward or back? If so how much, and if not which demo bindings can?
First you need to remember that any adjustable heel and toe demo binding will rarely have a boot centered perfectly on the ski. It will be off by a few millimeters. Would you notice it? Probably not.
If I recall correctly the toes of Marker and Salomon demo bindings adjust about a centimeter with each adjustment. The heel and toe pieces adjust independently, so you should be able to play around with boot to ski centering all you want for most adult sized boots.