Part of the problem is that I do not really know what exactly the shape is that I am trying to make the quilt conform to. If it were just a half cylinder, the problem would be easy and no darts would be needed. But there is a roughly conical section at each end. That's why rectangular quilts need to be cinched up. If you put darts in, you can make the quilt conform better to the ends, and it would not have to be cinched up. This should have the additional advantage of the sides in the middle section having less of a tendency to fall away from the hammock.
I was thinking that instead of using darts, one could use a separate fabric panel for each chamber of the quilt. Sort of like an old-style soccer ball or a beach ball. If you have a good idea what the shape you are trying to make is, the panel shape is still pretty easy to work out.
Where I get lost is trying to figure out how the panels would have to be cut for a quilt with different coverage along the length. One cannot simply taper the panels because the quilt will become conical, or at least I think that's what would happen. And that's where my head starts spinning every time I think about it.
I guess Grizz is the math guru here. Maybe he can come up with an equation and a program (hopefully not in perl) to compute the optimal panel design for a given hammock shape. But then again, he doesn't need much of a program to figure it out for his hammock...
Oh, btw, I just arrived in Albuquerque and went to Walmart across from the hotel to pick up some snacks. Of course, I had to stop by the fabric department. Got 10 yards of olive 1.1 ripstop with DWR. There are about 30 yards left, in case anybody is interested. It is the Walmart on Menaul.