I just used the GE SCS1200 silicone. On the previous page I showed how i cut all my rock so it was flat on the back so sticking it on there was pretty easy. I had to do only a couple pieces at a time and let it set then do another couple pieces. I held them in place overnight with clamps and wire strung over the eurobracing or with plywood shimmed up underneath them. I also put one of my big work shirts underneath them in case they fell before it was all set up.
I thought I had more pics but here's a couple when I started it:
