I build my stands with doubled up 1" ply, far more dimensionally stable than 2x4 (whens the last time you seen a perfectly straight 2x4) glass tanks are not very forgiving and it wont take much over 8' to cause problems. I suck at drawings but page 7 has pics of the platform for the 750, checked with a laser level it is within 1/32" at all four corners.
http://www.canreef.com/vbulletin/sho...t=55914&page=7