So, a mechanical question this time -

On a relatively short run of wire of fairly light weight (in this
case, 14 gauge stranded, insulated, and about 60-65 feet horizontal),
what's a good estimated counterweight for the far end? The wire
itself is light, but the counterweight needs to account for tension as
well. The support line is over a freewheeling pulley and is currently
tied off, but I think a modest eight would be better in this
circumstance as the near end of the line is a treetop with some sway
in the wind.

So, I ask if anybody has an idea about what a good weight night be to
maintain tension and avoid too much sagging. For starters, I was
thinking a simple barbell weight of 5 lbs or so more or less, but I'm
wide open on this one.

Thanks so much!
Bruce