Flying a spinnaker single-handed
The Tacker is a strap that wraps around the furled jib at the tack of the asym. The downhaul is attached to it alowing you to control the luff shape of the asym. Tight and straight for sailing closer to the wind and loose as you sail down.
I have been using this arrangement with a sock for about 10 years. You are right though when you say you need to blanket the chute with the wind in heavier air. I have never had an hour glass though. Wraps and hour glasses happen when you try to gybe the chute inside the forestay like a jib. The correct way to gybe an asym is to release the sheet as you turn and let the sail fly foward and proud of the forestay bringing it in with the other sheet. This eliminates most of the problems. If it''s really dicey you can blanket the sail then snuff it and then gybe and relaunch. Another thing I do sometimes with the sock is to snuff the sail and just leave the sock cleated to the deck while still hoisted. I then bag it at leisure at the dock. IMHO this is far less complicated and prone to problems than a Sym. setup with a pole, topping lift, after and fore guys etc. The only negative I see is the inabilty of the Asym. to sail as deep as the Sym.