I have a 3 ton Trane Central A/C and Heating unit, which I was told was a little more unit than I needed for the sq ft I have. The filter size is 20 x 24 x 1. I'm having a 450 sq ft addition put on and was told that I could use my same 3 ton unit. Would it be ok to have the intake vent enlarged to 20 x 25 x 1 since those size filters are easier to find?