Hey Tony, 
Well I had some of the same concerns when setting up my reef as well. 
This is what I ended up doing, I purchased a piece of black plexi($5) from a local plasic store and asked them if they you cut some overflow teeth in the top, I also had them bevel the edges for an additional $10. I knew by this point that I would simply cut off the back right corner of the tank at a 90 degree angle. This gave me a triangular overflow box of 6" per side. 
It works great, and best of all it took up a minimal amount of space in the tank. 
		
	
		
		
		
		
			
		
		
		
		
	
		
		
	
	
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