I got to do some playing with a RL today. I made my test RL from a piece of thinline Spectra I had lying about. I made it adjustable with a trucker's hitch.
What I did:
I set up my hammock (9'x4' gathered end rectangle) between trees a little further apart than I am used to. I gave it a fair amount of slack - more like I have seen on many recent posts - quite a bit more slack than I usually use. The suspension lines were about 30 degrees without weight.
Trial balloon 1) I set up the RL so that it was just straight with no weight in the hammock. I sat down. The RL drooped about a foot. I laid down and the RL became just straight with almost no resistance to a pluck of the RL. The hammock felt a little too banana for my likes. With the 48 in width, there was little room to put my feet to the side to sleep diagonal. My feet kept wanting to fall out of the hammock.
Trial balloon 2) I made the RL about 4 inches shorter. Now there was an obvious pulling up of the hammock ends on the support straps. I sat down. The RL was not tight, but it did not droop. I laid down. The RL was taught and it made a musical note when I plucked it. The hammock was even more in a banana shape and was more uncomfortable.
Trial balloon 3) I retied the support straps so that the angle was more like 20 degrees. A little closer to what I am used to. I set up the RL so that there was just a little change in angle of the suspension cords caused by the RL. I sat down. the RL was slack but not drooping. I laid down. The RL was tight - like the Hennessy. My legs were much more comfortable and I was lying flatter than before. The hammock felt "right".
I measured the RL and the hammock lengths. The hammock, with its end hems was 8'10" The RL was 8'2". The ratio was 92.5% From this, I gather that I like the hammock to lie much flatter than most of the posts that I have read. That may be because of the narrow width of my hammock.
It will be interesting to see if the asymmetrical foot box hammock I am going to be building in January will feel better with a a lower percentage (shorter) RL.