Greg,
Check out all Sump design here
http://www.melevsreef.com/allmysumps.html
I don't think you want to have water flow out of refugium and into the skimmer at all because that reduces the efficiency of having the refugium. If the last compartment must be the return compartment then i think you should put skimmer in first and refugium in second
I think with 3 compartments, the middle one should be the one contains water that returns water to your tank. The skimmers will be one side and refugium will be on other side
But i am no expert so let's see what others have to say