I tried heaving to with my SM243 and found that I couldn't slip exactly downwind as recommended by the Pardee's.  No matter what I did, I sailed forward at about 1/2 kt, which was fine for calming the motion, getting some rest and cooking, but I sailed out of the boat's slick to windward.  In a big sea it's my understanding that if you can slip directly downwind, the slick created by the boat will prevent waves from breaking on your beam.  I think that I would have to drag something on a yoke from the bow and stern so that I could adjust the attitude of the boat to be able to slip directly downwind.
 
If you figure something else out, please let us know.
Kent
S/V KRISTY
SM243