Very nice presentation!
So it looks to me like, except maybe on the very ends, you don't get near as much extra coverage going from 10 feet to 12 feet as you might think. What you get instead is extra head room with equal or slightly better coverage. Hmmm! Never would have thunk it.
However, there is another variable: hammock length. Would a longer hammock get more benefit and overall coverage from the longer tarp, due to being able to clear the tarp better? For example, my HH Safari has a 112" RL. Compared to 96" in your example. So, an extra 16" of hammock before the suspension heads up towards the tarp, allowing the 12 foot tarp to be hung lower( either hex or diamond) than with a shorter hammock? Of course, that hammock would also NEED more coverage on the ends, but a lower tarp would allow better side coverage, I suppose.
Or what about this variable: an 11 foot RL by 10 ft wide RECTANGULAR tarp, like the JRB? How might that compare to the hex tarps?
Handy dandy program you have there!