Eric the pieces of shade cloth I am going to use are about 6 years old. I used them for about 3 years to cover my small greenhouse in the summer but after I built the big one I am no longer growing plants in the little one. So from there for the past 3 years I have been using it to contain my compost piles that are ground up leaves and every spring when I remove it to move the compost to the garden I looks like new so with that in mind I think it is quite durable. It is also very strong you could make a hammock out of it and not have to worry about falling through it. If you go look at it has a small mesh opening which is sized dependant upon the percentage of shade it provides. I was thinking the same as you using thinwall sewer pvc. Figure I'll build mine and let the kids test it out before I put anything on it for growning media!

Bob