If you look at my built with a canopy I have 3 holes drilled in the back of the aquarium= 3 x 1.5 inches. it sounds like your option is to have four = V2 option. Then I am using a internal overflow box ( 48 inches long with a smooth weir x 6 inches deep and 2 inches front to back) ) and then a External ( 42 long x 5 front to back x 8 deep) - I drilled the External overflow box with 3 holes to connect it to the tank and internal overflow box via three 1.5 inch bulkheads plus drilled 3 drains (2 x 1 inch and 1 x 1.5 inch) in the bottom of it . I run the return hoses from the sump on the side of the external overflow box , into the back of the canopy, and then over the internal overflow box - then split it with one spray nozzle going low shooting across toward the back middle of the tank and one high enough that it breaks any possibility of a reverse siphon quickly. I am not a big fan of using bulkheads and drilling tank/overflows for return hoses- just me , but I think the possibilities for leaks, reverse siphon,etc. does not out weight the improved looks. I would drill another drain in the external overflow if I was to redo my setup so it would have 4 drains ( 2 x 1 inch and 2 x 1.5 inch). the tank is dead silent, but I am using both 1 inch drains ( one of them is controlled by a valve) and the 1.5 inch is left open for emergency.