Designing my own sump for a external skimmer the tank size will be 72Lx18Wx22H. The total amount of water will be approx. 105 gallons. Also the refuge will be divided in half for rubble on one side and the macro-algae on the other.
if you are putting a skimmer in the return section, I think 10" will be real tight. 10" seems real tight for the return section also, not much room for you to service and clean. otherwise, looks massive... nice!!
It may be more complicated but I think that I am going to try anyway. At the very least it will allow some extra room for a possible media reactor in the future.