Need help Drilling tank

[thanhjenn]

I was inspired by a reef members tank (Dez) so I decide to follow his foot step. Hope he doesn't mind. I have a new 135 gal and slowly piecing thing together. The tank comes with the overflow but want to convert to herbi overflow. As for the return I would like to drill various holes at the bottom 3-5 holes but not sure how to approach. Tank was bought from AI and made sure it is not tempered. These are my questions: on how to drill?, need to support where the holes are drilled?, how far apart (6 ft long tank), tank crack due to weight (drilling compromised strength)? what size hole? and any other things you could think off to help.

thanks

thanh