One idea I didn't articulate well is the idea/theory that each hammock has its own "sweet spot" based on the occupant and other factors. Like a tarp with cat-cut edges, if not pitched correctly, it will sag and fabric will be loose. When pitched correctly, all sides are taut.
My theory suggests that when the proper hang angle and diagonal sleep angle are matched with the hammock size and occupant size, the fabric will be appropriate taut on the sides.
That's not to say you can't sleep comfortably any other way, just that there is an optimal spot based on those several criteria: occupant height, hammock size, sag, and diagonal lay. Theoretically.
Thanks everyone for your thoughts and recommendations. I realize this is probably more theoretical than practical, hence the "Advanced Hammock Theory" -- maybe this is the 300-level coursework?