how about 105 G i love this tank
http://www.canreef.com/vbulletin/showthread.php?t=57734
FTS:
105G:dimensions of 72x24x14 trimless tank(with a 12.5" waterline) (will work for tangs
)
72"x36"x17" will give more aqua scape options, works out to about 140G with a 12 inch waterline
(180G with a 16 inch waterline)
and i would say external overflow as i really like them for some reason but maybe a dual one going to a refugium and one to the skimmer then meet in the middle of the sump for a return?
thats my two cents on a shallow tank