I have the 20 and the 5 hole frag rock. I love them as well. I have also seen "dougnuts" that are a clay ring with a hole in it and lets your corals encrust a large piece.

Favites and chalice should be fine really to grow naturally on the sand. They both create their own skeleton.

I also attach small pieces to medium small rocks so that I can place them or move them as I like. Mainly for zoas.