How high the hammock hangs from the ground? That is hard to answer with my set ups because each set up has so many variables. If I and my UQ are clearing the ground with 12 clearance once I am actually sitting in the hammock, I count it good for the night.
I prefer closer to 18-22" to be able to stand up comfortably from a sitting position, but the conditions of the hang situation, which stand spread how far, which hammock, which suspension, how my knees feel that day, all contribute to what is acceptable. If I remain suspended after all stretching, and can roll out at all onto a dry clean, safe surface, I can stand up. That is success in my world.
Everyone plays with the lengths to find their own ideal, so if you can, design for some variability. I try to design room for tweaking the setup as needed, because the portability and flexibility to fit many situations is very important. For a use it only at home stand, you can plan tighter.
Can't wait to see your final product.
Joyfully, and Curious in KY, Turtlelady