I have a blue ENO Doublenest. I went here: http://arrowheadequipment.webs.com/a...s/show/1099697
and got blue whoopies.
To change them out, un-knot the double rope that goes through the gathered end. Pull one loop out (the rope goes through twice). Tie the fixed end of the whoopie to the ENO rope. Pull the whoopie through the gathered end. Thread the other end of the whoopie through the fixed end and then pull tight. Do the same on the other end.
Now, you'll have an easily adjustable hammock.
If you want to add an adjustable ridgeline, get one from ArrowHead & just put the whoopies through each loop on the adjustable ridgeline. You can then set your sag.