You could talk to Grant at Big Al's (Burnaby and Richmond). He's built large commercial skimmers and I think has built some of the units at the Van Public Aquarium. He's set up a 12x8x4 tank in Burnaby that houses at least three btr sharks. You may reconsider all those tasty angels and tangs too
, I'm pretty sure he lost quite a few fish to the sharks.
PS: I like the "shark in the roof" idea, I just asked if I could have one and was promptly denied, she thought it would rot and start to smell after a while.