I've done the same thing with great success when anchoring and the wind and waves are coming from different directions (except that I take the line back to a sheet winch). It then becomes a trivial matter to keep the bow pointed directly into the waves. I have not done this in strong winds though other than the increased load on the ground tackle (due to the boat not being pointed directly into the wind) and a pretty heavy load on the sheet winch, I don't see a problem. I do carry a parachute aboard and while I've never had to use it, my plan is to rig it in a similar manner.

My recollection is that the Pardeys advise connecting the 2nd line to the main one with a snatch block. Anyone know why you couldn't just use a rolling hitch? That's what I use when using the technique while anchored.