I was able to sqeeze on 5 per shelf on mine once. I wouldn't do more than 4 though normally as you get a lot of fat build-up (potential for a grease fire) with so many. You should be able to comfortably do 4 per rack
Mike, I've done six over 9 pounds each. After putting on your rub,stand them on their sides in the shape of a triangle. One triangle on each rack. I did a little over sixty pounds once. Lot of meat!!!!