Excellent analysis! Every scientifically trained mind knows that it is best to only change one variable at a time, then evaluate the results. I subscribed to thread and bookmarked to share with people looking for a comfortable 1st hammock in future threads. Might be worthy of a "sticky" status.
I also generally agree with Gqgeek81's suggestion in comment #26, anyone who wants to "feel" the difference for themselves can take whatever gathered end hammock they have (or borrow one) and temporarily whip the ends with cord at various lengths to simulate the loss of comfort in shorter hammocks, including the ridge line if the hammock has one. (not all hammocks need a ridge line).
I own two "short" hammocks in addition to several very long hammocks, when i occasionally set up the short ones my daughters will totally avoid them. Even when they were young and short themselves and they fought over the longer ones. This is not rocket science! Obviously the "short" hammocks are lighter for backpacking etc.
BTW the apparently wasted material at the ends has been "replaced" with cordage for many centuries by natives in central and south america but not necessarily to reduce weight. The indigenous people (primitive but not Indian because they are not from that country) I lived with in the Amazon jungle collected wild cotton, spun it on their thighs, then wove it into fabric and made their own hammocks as they have done for hundreds or thousands of years. Conserving this precious fabric by using cordage at the ends instead of their handmade fabric was a major consideration. This cordage at the ends was also done by sailors on ships for several hundred years, possibly because washing fabric was not fun for them. I don't like multiple strands of cordage at the ends because it gets tangled and does not save much weight and also introduces multiple points of failure, but to each their own. Oh, it is is also a strangulation hazard for small children and pets, unsupervised. Dogs and cats love hammocks if you sleep in them every night and forget to roll them up in the morning. My pet monkey would jump on me every morning and rudely wake me up at daybreak as a kid.
Also that extra space at the ends and along the ridge line is not wasted, you can use it for peak bags and ridge line bags (your stuff sacks repurposed) and therefore store very little gear on the ground or hanging from trees where varmints and rainwater can more easily get to it.