Arrow pass at dimensional center yields a bow where the nock point most nearly bisects the string. The geometric implications of this are the same as positive tiller in effect, which is to offset the asymetry inherent in having the the nock point necessarily above the fulcrum of the bow hand. But in a practical sense we're only talking 1" or so here one way other other. Nobody buts arrow pass 2" above center (1/2 of a 4" handle), rather usuallly 1' or 1 1/2" above. Lots of wiggle room as far as I can tell but I see "even" bows as having a shorter upper limb. Seems like double dipping on the upper limb, forcing it to be both shorter and weaker, or giving the lower limb a free ride. At least that's the way I've reconciiled the issue for myself, although most of my bows wind up arrow pass slightly above dimensional center.