I also prefer to avoid polyester, resins, and any finishes, while maintaining high quality and easy needling. These are tough requirements, and every choice has pros and cons. I decided on Hobbs wool, because of the easy needling, good quality, and no polyester, and that I happen to have some. The yellow color won't matter under the linen top. I was iffy about having that much loft, and it contains resin, but I decided to not overanalyze this.
The new leaders for the quilting frame have been a bit of a challenge. The original fabric I bought turned out to smell really bad, and if anything, even worse after washing. Yuck! So, I fell back on some muslin that I already had. It's on the thin side, but it'll work. I have the leaders temporarily taped in place, ready for the final taping. I really wish I could avoid tape. Adhesives have some really nasty chemicals. But this frame has metal poles, and the alternatives I've tried so far are not really workable. So, I'm using tape with a metal backing, which should at least help prevent some of the outgassing.
This week is going to be very busy, but I hope to have the quilt on the frame by the weekend!