It used up almose three full balls of Cascade 220, and I used 6.5mm circular needles. I LOVE it, and I wore it to the grocery store today, out in 30+ degree temperature to get some photos of it in action!
you can see that using the bigger yarn and needles makes it a much bigger shawl then with laceweight, or sockweight. My Swallowtail is pretty much a full sized shawl, which is great, 'cause that's what I was aiming for!
I can't wait for cooler weather, so I can wear it everywhere. Meanwhile, it's being used as a throw on my couch, which is actually how I originally envisioned it used, and, it's already earned the hardest and most sought after praise available... Cat approval!