So I set up my AR with with a free standing rear sight and I put an aimpoint 512 on it. Currently my red dot is in perfect alignment with my irons. Having them all in line doesn't really bother me. But I was reading that a good co-witness should place your irons in the lower 1/3 of the sight picture. But I don't understand how you would have the same POI with your irons lined up below your dot. Also, for a red dot does the dot have to be lined up in the center to be on target? or is it paralax free and anywhere you see the dot is on target? Sorry for all the newb questions, but I've grown up with scopes and irons, and this hole red dot is new to me.