I have decided that it is time to drop those extra pounds. I am building a G4 backpack and ditching my 6 pound pack. I packed away my Whisper Lite Internationale and aluminum cookset and made a gramweenie kitchen like Tinny sells. (sorry Tinny, I perfer to make my own.) I am making my own tarp, and I was wondering about a ground cloth. do I really need one? If so will 2.2 oz ripstop nylon be good enough?