New 60 gallon tank build

[guitarfreak11]

Ok, so i have a 60g acrylic tank with stand and soon canopy. Dimensions are 48x15x18. I bought a 2x150w with 4 T5 actinics mh fixture off of Bill on here and i have one halide hooked up so far(still need the second). I am pretty sure they will be enough as long as i keep them low. I will have a euro reef rs 80 in the sump, a fuge, and the return chamber. I think the tank will be a 29 gallon. Not sure yet so we will find out. I have 46 inches underneath the stand so yeah, and i have 12 inches width to spare. I will be adding an overflow and drilling the tank. I will be drilling three holes. 1 1.5" drain in the overflow and 2 1.25" holes in the back wall for returns. Or should i go smaller for the returns? they will both be hooked up to dual loclines and plumbed to my scwd. I have one koralia 2 and can easily access another if needed. I will probably put 80 pounds or so of live rock and 60 pounds of live sand in my tank, rubble and sand in the fuge with macros. The fuge light will either be an 18w or 96w depending on if i want to make the fuge a frag holding area also. So....here is an autocad drawing of my plumbing.

[guitarfreak11]

Also, i am curious, how many GPH goes through 1 1/2 inch drain compared to a 1 1/4 inch? And since im putting 2 return holes what size should the loclines i put in them be?