[Tangster]

I'd not drill any hole in the top of the tank I always drill mine low and put a vertical overflow box then I use a stand pipe behind the overflow to control the distance the water through the overflow has to fall to drain to the sump limits the splashing sound and if you just try to use the bulk heads drilled into the top area of the tank you will never have a totally clear skimmed water surface and you will not be able to control the water line as it will be lower then the top band of the aquarium. I would suggest that you go look at a reef ready system and notice the overflow column boxes . There is a reason its done like this.