Getting my tank drilled tomorrow

[tg1119]

I am getting my 40 gallon drilled tomorrow and wanted some input on my over flow. I was planning on doing a center overflow. I can't find the name of it but I would like an over flow that goes only about 6 inches deep in the tank instead of going all the way to the bottom of the tank.

Does anyone know any advantages/disadvantages of the style of overflow vs. a normal style overflow?

Like this but not the whole length of the tank.

Thanks
Todd