how much is to much? (waterflow)

[Zerandise]

I have over 4000gph on my 140 and i know i could use more in spots. 1 1/2" wont do 4000 tho.

http://www.reefcentral.com/calc/drain.php

will tell you how wide the hole must me to handle flow. It says 2.6 for 4000gph.