Thanks for all the replies! Denis asked a very good, probing question. "What is the planned purpose of the BOB?" To be honest, I don't anticipate sleeping outside. So my shelter needs are of the "just in case" variety. So I agree that does favor a tarp. I found an inexpensive one that might work, the larger 11'x11' size here: http://www.sportsmansguide.com/net/cb/guide-gear-11x11-tarp-green.aspx?a=954701&e=Y

I'm sure this tarp is mostly junk, but it does have more and better (sewn) tieouts than the typical cheap grommet blue tarp. It's inexpensive, and might be serviceable for my "just in case" requirements.