I'm building a tank for our Bamboo and pair of Coral Catsharks that isn't much bigger of a footprint than what you already have. I'm going 8' x 4' x 2'. They are currently in a 300g which I think is the limit at their sizes now.
I really want to get an Epaulette Shark Egg right now for my wifes class to study and hatch this year, but coming up short on finding one. For the last 3 years her class has been studying Bamboo and Coral Cat eggs to find out what kind of shark egg it is and when it hatches the kids learn about the shark. By summer the sharks were the perfect size to avoid being eaten by our grouper we have home when moved from the classroom 40g Breeder tank to our main tank at home.
Mines not build yet either. I'm in the process. Just finished cleaning out the area the room will be and then need to start framing. Once I get the left side all set, I can start on the tank. I actually increased the tank size to 8'x4'x32" as I figured out a way to do that and still make the space work. My goal is to have this done by September 2018....we'll see. Where are you in your process?