You make the PVC structure the way you want it to look. (don't glue them) Use Elbows, Tee's and short pieces of 1/2 or 3/4 pipe depending on how big or rocks you're using. form a base with the PVC so that it will sit on the bottom of the tank nicely, and build it up toward the top of the tank. It's really quite easy.
And then you simply get a bag (or in your case 9 bags:D) of tie straps..
You can either drill holes into the rocks, or in most cases, your rocks have enough natural holes in them to push a tie strap through it, and hold it securely. Then you simply wrap the PVC pipe with rocks..
It's easy, fun., and durable as hell.
You'll love the look of it, especially for a double sided tank...This way you don't have to lean anything up against walls.
Here's a link in case you missed it..This will give you an idea of how to do it.
http://marcorocks.com/index.asp?PageAction=VIEWCATS&Category=49
NOTE: DO NOT USE WHITE TIE STRAPS.
Here's why..The Sun, deteriorates white tie straps, and they break...I don't know why, but it does. I assume with the amount of light our tanks need, our lights would do the same.
So err on the side of caution and use
black only.