What's with the 7 ft water depth?
When designing a tank for sharks the water depth is usually the smallest of the measurements. Most shark tanks are much longer and wider than they are tall. Just look at most Public aquariums, which have sharks in them.
For a 4,000-4,800 gallon shark tank, instead of something like a 12' x 7' x 7' - how about a 18' long x 9' wide x 4' deep oval tank. the latter design would better for keeping an adult smoothhound - or you could even keep a few juvenile ORVs in that tank for a couple of years(although they would still need a larger tank before they reached maturity).