When I read stealthy camping and think tarp I envision something along the lines of what snipers use in combat. A ghilly suit for your hammock, using natural materials found near your campsite. Depending on how stealthy you wanted to go you could do a double layer hammock with a camo base and then some type of mesh that you could layer with local brush once you get to your site. It wouldn't have to be perfect as the camo base would help break up the pattern. And when it was time to go you shed the natural material you used, pack up and go. But you guys/gals have been doing this a lot longer than I have so my idea may have huge flaws I haven't thought of.