How deep is your hex? Using a canister on this volume of tank is absolutely appropriate. Using an HOB on it will require a long intake tube to reach the bottom and enough power to draw it up to the HOB's filtration. Another problem you may run into is, depending on the length of each section of the hex, would it be wide enough to hang a decent power filter from. I would really rely more on a good canister than an HOB in this situation.
One other thing to be aware of is that the surface area of water in a hex is much less than an equivalent surface area for the same volume of water. This does mean decreasing your stocking estimates to match the surface area you have to allow for less area for oxygen exchange.