I had been doing some anchor research and came across the Mantus. I didn't see that it been discussed on the forum before. Owner/users really seem to like it and watching the test videos, it seems to hold better than any other model.
The testing was done in sand and mud; I don't know how effective it might be on a rocky bottom. The tests were performed without an anchor chain but it didn't seem to matter with the Mantus. Here is a link showing a quick test video. The first one is against the Ronca...
http://www.go2marine.com/product/327...available.html