Dont do it on your own.I use an asymetrical all the time and start bringing the sock down when speed /wave action starts digging the bow have ran steadily at @15 knots on long passages with about a 2 thirds of the sock down in plus 20
wind.The main times for problems are with the
wind too light If you let your
spinnaker out in 8 knots as suggested within a few seconds your
boat speed will take up the wind speed and douse your
spinnaker and Murphys law puts it under your bow and out the back tangling on keels rudders props.Make sure you have at least 10 plus before letting sock up then boat speed vs drag should keep it tight.Great fun ,great speed and easy on the
helm.But dont do it without either
autohelm or better still ask someone to come take the
helm while you try it out If THE LAW kicks in you will apreciate the extra pair of hands and probably save a sail.When the wind picks up you need to be able to start bringing the sock down to keep boat speed down and avoid the old p.p once again necessary to have a helmsman or auto.Once you get it right nothings faster or more thrilling as you get up to wave speed and surf for long stretches.East coast Aussie
trade winds enable us to use on long passages and have used for ten days straight without needing the
mainsail.Great for covering long distances fast.Good luck Geoff.