Sample00 ... I thought of something else that might be useful. You were wondering about using treated lumber to edge the patio. There's a product called "brick stop" that works excellent for this. It's made of either plastic or aluminum, and it an edging the you spike into the ground which contains the perimeter of the patio stone or bricks. Our patio has been down for seven years now and its edges are still straight a ruler. It's completely invisible once the patio is finished too. The down side is that it's kind of pricey.
Here's a link about the stuff:
http://www.brickstopcorporation.com/...n_anchors.html