help me build a sump

[yellowtail]

i was thinking about make a sump with baffles. i was hoping to get a ER skimmer in there which i have in my sump now but it fits only by a hair. so if i got a 20 long what would you reccomend. i would like it to have a fuge, place for skimmer, and place for the return pump(mag 7)
by the way i have a 40 breeder Display and the dimensions are 36Lx18Wx16H
keep in mid this has to fit under my stand

 

[essop3]

not sure what measurements you'd need but I like this design.