Originally Posted by bear bag hanger
Don't know much about nylon vs taffeta, but if it's true that taffeta is heavier, then I'd get the nylon version. Stick with the double layers. You may find that using double layers with a pad to be more than acceptable and not get an under quilt. Under quilts are more comfortable, but usually more expensive and heavier than a pad and extra layer in the hammock body.
Nylon and polyester are tricky things. Comparing the fibers, here are some observations:
Polyester is a superior fabric in these regards: it has a higher burn and melting point than nylon, it has less stretch than nylon and it doesn't stretch when wet like nylon. It is also more UV resistant (not the color necessarily, but the fabric doesn't break down under UV light as quickly) and polyester is stronger for its weight than nylon. It's also absorbs less water than nylon (nylon absorbs a little while polyester absorbs none into the fibers themselves, though water can be trapped between the fibers). For this reason, polyester "dries" faster.
Why does everyone use nylon? Why would anyone WANT to use nylon?
Polyester is usually more expensive than nylon and, thus, not as widely available or used as nylon in a lot of applications. Additionally, finding particular styles of polyester can be difficult. I've tried and tried to find an affordable polyester ripstop fabric, but it's impossible unless I bulk order from China.
While I definitely agree that many polyester fabrics are heavy, all are not necessarily so. If you had a 1.1 ounce polyester ripstop alongside a 1.1 ounce nylon ripstop, the nylon fabric would have a lower weight tolerance.
I think people of my generation who remember godawful polyester suits and women's pant suits from the 70s have a (justifiably) poor impression of the fabric due to its overuse in garments once upon a time. That polyester suit I had to wear in the family portrait in 1976 took me at least 30 years to get over.