Thanks for the suggestions, comments.
thegrun - sounds interesting, kind alike a circle of top archways if I am understanding, let me see if I have some more rock to play with. I have 2 pieces from my bleach/acid wash I havent used because I didnt like the look.
miPapareef - I have used hangars and holes to keep the rock in place, I am going to have the 3 main parts so if I need, I can take those out. I am going to use wetweld on certain pieces to have a second bond or on the light pieces, or bottom wedges for addtional support to make sure the base rock doesnt cradle back and forth.
domb54 - Carboard was what the tank sat in when shipped to me. I am making sure when I place it that I have enough room to get in and aound it as well as my mag float can get to the glass. I am doing bare bottom and will not be scraping the bottom clean, but will do wipe downs if needed.