I've come across another option. I will not be able to try it until next week. (Company coming and I must clean house.)
While looking for places to stash all the scraps I've been sorting for color, I ran across a large piece of leftover curtain sheers (made "cafe style" curtains for an unused bedroom, and wanted it to be bright) . Of course, it's 100% polyester, so it's slickness might make it unusable. I washed it with the sheets and it's really lightweight and pliable. I'll see how it handles when company is gone.
This quilt is what prompted this search for a perfect foundation for a string quilt.
bkay