Proper position of the AVC valve on a 120g Flex-Lite tank?

My tank has two bungs on the side. One about 1/3 of the way up and one half way up.

Which of the two will give best performance? I have a 2hp pump in a submerged 4" well.

The well guys installed it in the bottom port. I believe this is incorrect and that allows more air than necessary in the tank, limiting the water stored.

Any opinions or pointers to white papers or instructions on this?

My old tank had the bung and AVC half way up the tank.

Actually the more air in the tank the better, as long as it isn't coming out of any of the faucets in the house. More air means more gallons of draw down from the tank.

I've seen them in both positions, but most guys around here put them in the upper port.