Thanks for the information, David. There is another company that I've seen advertising recently on HGTV for an under-deck watershed system that's intended to keep the lower patio dry. It's called Dry-B-Lo and looks interesting. Here's a link:
I don't have any experience with this product myself, but it looks as it seems to be intended to retrofit pre-existing 2nd floor decks which might be a great labor-savings.