norwood 6? really? or do you mean norwood 5?
7000 grafts on a norwood 6 guy, id say in those cases the hairline is dense but the more you get closer to the crown the less dense it gets and the crown almost always has the diffuse thinning balding look or is left completely bald, so in regard to the crown its not even an illusion of density anymore
and the dip behind the crown? there wont be any folicles left to cover it. even in that famous irish guy who went to eugenix and has a terrific result they let the dip untouched and hoped he gained hair there with finasteride (which he did), if i remember correctly.
so to get full coverage at that norwoodstage id say you need at least 12000 grafts, depending hair characteristics etc of course. otherwise you need to make compromises, by letting the crown and the dip (more) bald or starting the hairline basically at the midscalp.