I've got a 130-foot doublet hanging 90 feet up in the air between two
trees. A pulley and a counterweight (a gallon of sand) keeps 20-some
pounds of tension on the line. Not a lot of tension but works great on
non-windy days. If the trees were stronger up at the top I
might try a heavier counterweight, but I'm not sure I'd be comfortable
doing this because I am really hanging from the treetops right now.

The feeder is approx 70 feet of 450-ohm window line (like twin-lead
but with little gaps every so often) to a standoff on the side of the
house. Yesterday when we were having 50MPH gusts this was billowing
out like a sail. I had twisted the window line a while back after the
last big windstorm, and that seemed to mitigate the sailing-ship kind
of effect, but not by a lot.

The counterweight and pulley did a great job of absorbing the wind
gusts. It was really impressive - when the big gusts came up, the
feeder billows out, and the gallon of sand shoots up in the air 30 or
40 feet above its usual position. I'm pretty confident that as long as
the trees didn't fall over in a hurricane, this antenna would stay up.
I even put a real stainless pulley with bronze bearings in, replacing
the one-dollar hardware store pulley, and am happy that I did. I have
seen the one-dollar pulleys get visibly corroded in a year or so on a
previous antenna.

But I'm thinking... if I just used two conductors of #16 copperweld
and some spacers to get true ladder line as opposed to window line,
would this billowing completely disappear, or drop to a tiny tiny
fraction of what it is now? Or would it just continue billowing the
same way?

What's preferable for such homebrew ladder line: solid copperweld,
stranded copperweld, solid copper, stranded copper, ???.

Tim N3QE