I'm thinking I'll try what's available first, and then decide if there is a need for custom webbing. Like many ultralight applications, we may find that current materials offer reasonable durability with adequate weight saving by using non-typical materials (RS nylon vs polyester webbing). Using less material (ie no more than is required for safety and reasonable durability) is the easiest way of achieving light weight. Just look at the trends in backpacks over the last thirty years!

Jungle Jim