I only run the Lev IV stand alone plates. I don't want the extra weight of the backers and I don't wear the side panels, just front and back plates. I prefer the mobility of just plates over the limited Lev III protection in the sides and it also keeps me from adding more stuff I don't really need to my kit. Regarding the backers...I've never worn them for that purpose so I can't comment on them other than the added weight. Resale of Level IV stand alone plates is generally better from what I've seen if I decide to get rid of them.