It seems that what it does is keep the middle of the fabric centered all the way across, which results in a higher tension in middle of the hammock and then as you proceed from the center the fabric get looser. Basically a variable tension system.
Edit: I followed the exact dimensions of the Backpacker. 120" fabric 100" ridge. I sewed tubes at the end of the hammock like HH. I then ran a ridgeline through the tubes. I wasn't confident that the ridgeline would hold just by the whipping and a not at the end, so I decided that a sheet bend was the best option for hanging the hammock.