Thanks to all for your input.
Randall, that poncho mod sounds like a great idea. I was planning on sewing a sil/DWR/noseeum bivy using the meteor pattern or a modified version of the Oware drawcord when I started thinking about this propore stuff. Dual use as a poncho and bag cover just makes too much sense not to try and I can take along my bug pyramid when necessary, for 12.99 I think I'll order one right now.
One question, do you ever get any condensation on the bag using this setup?