Deac,
I'll give that one a go next time I'm out - 15 feet down the anchor line, bridle back to the stern cleat. More difficult to do on a permanent mooring - but certainly not impossible. Its just about getting convinced that it works.
I tried the secondary anchor line ......about 15 feet down the anchor line and then back to the stern cleat. Reckon it improves the "hunting" at anchor quite a bit. It makes for a different kind of boat movement......kind of jiggles about and cuts down the angle of the swing.
In this case I was anchored in fairly shallow water, so I used a shackle to attach the secondary line to the anchor line at my join between anchor chain and rope. Seemed to work well enough. I'd like to try it in a bit more wind to see how it goes, but so far so good.