Kasey,
I have seen the shimano video on their pet rocks. They go pretty light and soft. We fished them on jigging gear and 50-70lb braid. The cod and Nannygai we were catching were up to 15 kg and they put on as much of a stink as mid range AJ's. We also replaced the hooks with 5/0 assist.
I think they are also designed for deeper water than we are fishing. We are only in about 40metres. I did some jigging in Canada for silly little rockfish, anything under 150m was shallow! Pet rocks over there would be very effective I think.