What you want is the anchor to lay flat on the bottom so the flukes can bite in to the bottom, when I had my full size sail boat the first 25' were chain and the rest was rope. If I was worried about the anchorage I would do the same thing that they used to do in the time of sail with a large ship and that is to put a second anchor at the end of the chain who's whole job was to make sure that the chain laid flat on the bottom and the pull on the main anchor was kept parallel to the bottom. You get in to problems when the anchor line or chain starts to put an upward pull on the anchor and the flukes come out of the bottom.
Andre
over yonder in Portland Oregon