I'm just building one that same size myself. I'm taking my layout from the
advanced acrylics sump of the same dimensions.
I'll pass on the filter sock because I'll place a sponge between the last 2 baffles instead. That way I can fit a larger skimmer in the first section and I'll get more organics into the fuge section in the middle. I can rinse the sponge every couple of days and avoid having to bleach filter socks. Just my personal preferences.