I have seen a picture of three under a tarp in someone's gallery, so I know people do this...
My buddy and I will be doing overnighters with our hammocks, and I am debating on whether we should go with one big tarp or one for each of us. I made a diamond shaped tarp that I think would be adequate for bringing when I don't expect rain (just to be prepared). But thinking back on some of the Kansas storms I have wethered in tents, I know I need more coverage and tieouts on my next one.
This is what brought me to the big tarp. I think I would really enjoy having one tarp because it would give us a large space that was weatherproof to hang out in. The only problem I can forsee is that having to share a tarp is going to make finding a good site more difficult.
From your experiences, do you think it would be wiser to share a large tarp or use two individual tarps?