I realize this may seem simplistic, but where you put your overflows has a lot to do with what type of fish you keep, and your style of maintanance.
Although I have some tanks with standpipes (drilled on the bottom), a few drilled on the back, and my preferred spot, drilled on an end, with upturned elbows, and carved weirs.
Because most fish I keep are riverine, I like to have water flow down the entire length of the tank, and exit the other. I also don't like stand pipes, because they get in my way during maintenance.
I drill holes to fit 1.5"PVC, it isn't as easily plugged as smaller bore pipes.
Here's an example.



Although I have some tanks with standpipes (drilled on the bottom), a few drilled on the back, and my preferred spot, drilled on an end, with upturned elbows, and carved weirs.
Because most fish I keep are riverine, I like to have water flow down the entire length of the tank, and exit the other. I also don't like stand pipes, because they get in my way during maintenance.
I drill holes to fit 1.5"PVC, it isn't as easily plugged as smaller bore pipes.
Here's an example.






