Why not build whoopie slings as continuous loops? At least, as an option or alternative to the "straight line" model?
Seems it would be stronger, because as a loop, the whoopie would never get down to a single length of line anywhere, not even for a couple of inches. It would always be "doubled." And it would be more adjustable (could be made even shorter and perhaps even longer), since there would be no locked brummel taking up room. At no greater weight.
Alternative number two: why not build a single continuous whoopie sling, from one end of the hammock, to one tree, across to the other tree (doubling as the tarp line), and back down to the other end of the hammock. Again, seems it would take no more line and might even save line and weight and would need no separate tarp line.
Hmmmm. Can anyone tell I got out of my box today?