I finally have all the pieces I want for my tarp suspension. I briefly looked around this forum to see if anyone else has already posted the same setup, so I apologize if someone has done so. This setup relies on the mini line-loks (aka clamcleats). They add the capability of very easily repositioning the tarp over your hammock, or just sliding the tarp off to one side without having to untie the suspension. I forgot to include a picture of the figure-9, it's in lieu of a knot on the other tree. These are the components.
small biner (optional; avoids having to tie a knot)
small figure 9 (also optional, for the same reason)
3mm mason's line
a rubber band (helps maintain tension)
2 mini line-loks (http://www.cleats.co.uk/home/details.asp?id=7k)