Sump & filter socks - 4 or 7 "

[hfp75]

I am about to design a new sump for about a 125g tank. I found a Hagen 75g (48x18x21) tank for $50 bucks and am in the process of drafting the insides.

My debate is filter socks... I am gonna try to add in socks for filtering. I dont want to commit so much space for a pair of 7" socks but at the same time with 21" am I better to go with 3x-4x 4" socks across or 2x 7" socks ? the 7" socks will take more space (3" more) across the sump than would a row of 4" socks.

anyone?

I am currently using filter floss as a filter in my 20g sump... it works but is a hassle to get in and out. The socks just dropping in the holes will streamline replacement..... socks seem like a good idea....