WOW-- so much good thought here.
Jim, thanks for the vote of confidence-- I'm pretty much all theory on this facet for the moment. I like round line for the reasons you cite as well. Also, it's cheaper-- and it doesn't have to lift a car, only you, so figure anything at about 4 or 5 times your weight should be enough in terrible conditions.
Fred, I'm glad you learned that lesson under ideal conditions! Personally I hate that white-coated lifeline stuff. For the reasons I mentioned above, do not be afraid of decent-quality yacht braid. The wire, especially in that plastic coating, can give you a false sense of security, same as it does for lifelines. What's going on inside that plastic? --you won't know till you don't want to know. My lifelines are 5/32" 1x19 rigging wire with no coating. And you have already learned that attaching terminals is a process specification that's very easy to misjudge and get wrong.
Kettle, thanks for the warning about avoiding going overboard. My problem is that the boat is so narrow (8 ft) that I can't put jacklines far enough away to accommodate the reach of a 6-ft tether. I thought of just running one down the middle, but the hatch hood and spar are in the way. I have seen people run none at all, just find separate attachment points-- one sailor (I forget who) attached to the vang bail, the mainsheet tackle, the spinnaker slide, anything. Really this isn't such a bad idea-- after all, all this stuff is on center and if it's cast-stainless it's certainly strong enough.
I think I'll wait till I get the halyards strung first. On my boat the halyards pass through tunnels in the molded coaming, so it's crucial for them to align perfectly to avoid chafing on the edges of the tunnels. At this point the jacklines are a secondary concern and can be accommodated even after the deck gets painted.
Thanks for all the thoughts, mates.