Panels, like those, are basically "sandwiched" against the glass by strategically placing a couple of "base" rocks against them. I've never had any fall while they were set up in the aquarium. One tank has had them in it for several yearw now.
A lot of people seem to be trying the "salt recipe" lately. I didn't use any in mine and love them. They're easy to make and have all the porosity that they need. My rocks have been in tanks for quite a few years now. Also, I keep sps, lps, and softies without any problems.
crázy clowntang, one of the main complaints with incorporating salt into the recipe seems to be that it creates rocks that are more brittle than some people would like. Personally, I don't really think that it's necesary to add the salt. It does, however, make some interesting surface features on the rock.
Anyways, good luck with whatever recipe you follow and have fun with it. -Mike