I would doubt very seriously if that were the case. Antler billets don't really need added weight, if you don't have a lot of mass, you can make up for it with billet speed. I do a lot of knapping with small whitetail antler billets. Also, I think a lot of the aboriginal knapping of NC materials was done with hammerstones and wooden billets, both of which have plenty of mass. Plus, the shape and form of a bannerstone doesn't lend itself to attachment to an antler billet. I'm not even convinced that they were atlatl weights. If you can find a diabase dike (there are a lot of them in eastern NC), the diabase makes good hammerstones, as does sandstone.