am having a 180 gal tank built and would like to ask some advise on the built in overflow box. how much clearance should i need on the lip of the built in sump to the top cover? should i have 1 or 1 1/2" grill to drain water? how big should my drain be 1 or 2"? last... since i want equal returns on both ends of the tank and only one mag-drive pump...is this possible? what size should i use? 3/4 or 1/2 on each side? kinda a lot of question... don't wanna mess it up. 
any web links would really help. wanna have a flow rate of at least 1200gph
any web links would really help. wanna have a flow rate of at least 1200gph