Replying to Anyone who knows how to mount skis? or some help about how to figure out true center

so i have some older spaceframe 1080's and i plan on getting new skis soon anyway, but i just took off my bindings just to try to learn how everything works and whatnot and it seems pretty simple. i was also wondering about how you mount true center. theres a line on the ski which is what mid sole? and the back holes of the fron of the binding are 4 inches from that mark and the front holes of the back part of the binding are 6 inches behind that line, so if i moved each 1 inch forward so it was 5" and 5" would that be true center? i dunno im confused but i want someone to explain it to me, i know its probably much eaiser to just take it to a shop but i like to do things myself. thanks for any help.