I am getting ready for a air handler with a variable speed fan.

It is a 5-ton unit and my return is a 24x24 grille. I've read some stuff on here that says that too much pressure/restriction could hurt the life of the motor.
I know most of the pro's recommend certain "tests" to determine capacity, etc.. but I've never seen or heard of any of the companies here doing that... at least on a house that has already been built and has central a/c. Maybe it is an area thing?

Anyways.. I feel certain the installer will say that we can do whatever I want on the return and leave it at that... Is that a big enough return for this size of a unit. I think my only choice would be to put another return on the other wall if it is not. This unit is in a closet that is on a corner in the central hall.

The unit was previously in the basement with an even smaller return, but a duct leading to a floor grate in another room to provide additional input.