I don't know about bad plugs, but I saw something above about action of the AC. I believe the good action is due to the the wood being tapered, large diameter in the front and small in the back. I would say the wide front causes an over-exagerated wobble and produces low pressure behind it to let the tail work with minimal effort. The large and probably unintentional gap in the body segments probably also helps. I may be wrong but I thought the AC's had a tapered body, The one I made did. And Yes the AC plugs seem or look like garbage. The Plug I made and tested in my pool had a awsome action and thats action is probably why they work.