Sorry- I don't know about that- I'm not much of a MYOG guy. But if you do a seperate post with the question, I'm sure a reader will have the answer.
I'm with Inaki- A simple rectangular tarp, although not as cool, will suit your needs well. And a lightweight carbon pole would be very nice for not much extra weight.
Personally, I'd look at tarps from Mountain Laurel Designs, Gossamer Gear, and from this site. If you spend your $ on a tarp made out of spinnaker or Cuben fiber (Spectralite or Nano) you will have a tarp that is so light that you'll be able to carry a pole if you need to.
Just an idea. I'd sure love to see your finished product- that's for sure!!!
Best of luck,