Drain size question

I recently purchased a 90 gal tank that has been drilled once. the hole is just over and inch which equates about a 3/4" drain after the bulk head is installed.
Is this going to be adaquete fora 90? I am leary about drilling again, and really dont have the tools.
i was thinking i would prob use a mag 7 or 9 as a return.

 

The water will flow as fast as you can pump it. you will probably still need a ball valve under the tank to slow the flow down. If you don't use the ball valve it will be VERY loud. Adjust the valve according to how big of a pump you get. The more water you pump up the more water will flow through and gravity will pull it down as fast as you can pump it regardless of the size of the overflow. It might just have more pressure than if you were using a larger bulkhead.

 

I think it could be good good for about 200gph more if it is in the bottom and the plumbing goes straight down to the sump.