How many holes is too many?

[mr_alberta]

Excellent! Thanks for the replies thus far. One last question, would that overflow slot at 16" long x 1 1/2" wide allow enough water to flow through at a given point to have my closed loop inlet in the external overflow box? The pump would be either an Ampmaster 2700 or Sequence Dart.

If not, how big would the slot have to be? Anyone have a formula on how to calculate flowrates for things like this?