FYI, I have postponed my Defender order because I may need more bottom paint. (It took more to coat my boat today than I expected. Need to wait and see how the second coat goes on tommorrow.)
So I have some more time to mull over harness/tether decisions. I've gotten some great advice here on what to get and how to deploy it, so keep the suggestions coming. Obviously some of the suggestions contradict others, so I can't follow all of them. But I can combine suggestions into a hybrid approach that fits my boat. For example, right now I think I'm going to get a dual tether and run dual jacklines down the sides of the boat. If I have to work near the mast, I'll clip the 6' end onto the jackline to windward while I go forward, and the 3' tether to the base of the mast once I get there. If I need to work near the bow, I'll clip the 3' end to the windward jackline, and the 6' tether to the mast, unless I need to go all the way to the pulpit which is 9' from the mast, so there I'd need to use just jacklines.
In addition to buying a top-quality tether, I may build my own that's shoter than 3' for specialized needs.
I also tried to call about the MTAM safety course, but it conflicts with my planned launch date and with a commitment my wife has (I want us to be trained as a team), so I may have to wait until next year.
So if you get hit by a wave or the boom and your jackline is along either side of the boat and the teather is either 6 ft or 3 ft what prevents you from going through the lifelines and into the water or hanging off the boat close to the water. Clipping to windward when a boat is pitching side to side doesnt insure anythiing as the windward may not be the direction the motion throwing you off the boat is from, it may be a wall of water moving you toward windward. It may also be incredibly awkward clipping to windward if you have to work on the lee side of the boat.
Even if placed along the side it should be within the rigging and along the coach roof. Thought also must be given for clipping in once up the companionway and around the dodger if one is present without being totally unclipped.
Most people walk up the gunwhales so this will be under your feet
I prefer my Jackline to be fairly taught. Thats easy to do in a straight line.
Before you rig this way I strongly suggest you take the safety course and observe others so as not to waste money.I would also rig some temporarily both down the sides and also centerline once you have the teather and practice.
IMHO there is no windward/ leeward when there is something which needs to be fixed. Its usually better to go the indward side because its higher, but in rough pitching seas, that may not make a difference