Success! The colors in these images aren't quite true, but they're close. The 3rd one is a lot darker and the blue markings aren't so obvious. But it worked. I think I would have gotten an even more deep purple if I had the patience to let the dyes work longer. But then maybe not, some of the dyes were quite old. The 3+ yard pieces were so unwieldy I decided to do the rinse in the washing machine. So after unwinding them, which was a struggle not splashing dye all over the place, I put them in the washer and set it to rinse with cold water. Oh so much easier. Then added the Synthropol detergent and ran them through the wash. The final rinse wasn't quite clear, so it got another rinse run through. I haven't ironed these yet, I was hoping a mangle would show up on my doorstep, but I don't think that's going to happen.
This piece is going to be the binding. It will end up as about 400 inches long. Something else I'm not looking forward to pressing.
But I'm thrilled that I'm not going to have to wrestle this through my sewing machine. The quilter has booked me for mid-March so I will just have to be patient until then.