I have made a guide rope with 2 clips one tied to each end
The length is adjustable so once you have found the ideal 'dangle' you like on your hammock you can lock it off and the easily reproduce it in the future. This is a std catch 22 situation - you need to have set up the hammock once in a way you like to get the length but once you have it is easy to get the same setup every time
Step 4
Clip one end of the guide rope to one ring
now clip the other end to the other ring
Step 5
Repeating step 3 pull the loop through till the guide rope is horizontal and taught - your hammock will have the perfect sag at this point