i have a plan for a 50 gallon sump if you wanna look at it, you could make in more narrow and/or shorter to fit your needs. it is in the
diy forum.
http://www.aquariumadvice.com/viewtopic.php?t=6174
that is the one. there are pics and all, like i said you can modify it to make it fit your stand. to calculate your gallons in your sump just do lxwxh and then divide by 231.
hth