i dont see why you would need two overflows but the one that you were looking at was way to small. I have a 135 fowlr
that i just finished setting up. i have one overflow that has 2 1.5 inch outlets that has a 1500 gph
flow rate. i have one return pump in my sump that runs at 1720 gph
but only about 1450 when pumping up 3.5 feet. I also have two 650 gph
powerheads on either end of the tank. circulation is great and there are no dead spots. my turn over rate is just over 20. you will need another powerhead for your skimmer,most come with them but if not it will tell you what gph
rating to get.