Hi,
The refuge are is approx 19 x 12 wide and would be about 8" deep in water, so pretty decide area.
I'm not sure on the flow though. Looking at the layout i think you could push 700 plus gallons through it, but not sure if that is too much to keep your refuge area from blowing around. You might check with cprusa.com and see if they can give you more specs.
The skimmer is quite small too, but used with mud and algae, you won't need too much skimming.
For rating, this is just my opinion, but i would think about up to 90 gallon tank.
thanks
jason