I have a 3 ton split heat pump for the upstairs of my home. At on end of the upstairs, I have a 20x16 air return. At the other end, I have a 35x13 room that has a 24x14 return. I'm getting ready to raise 2 walls in the 35x13 room to effectively make 2 rooms. One of the walls falls right in the center of the existing return, it has to be moved. I was thinking the best thing to do would be to move the return over and keep it in one room and then add another return to the 2nd room, that way both rooms have a return.

I called a local HVAC contractor to get a price to move one register and then add another return register in the other room. He said they would add another 24x14 register to the 2nd room (that way I wouldn't have to buy a different sized filters).

Questions are:
1) Will adding another 24x14 return mess my system up (too much air return)?
2) would the proper thing to do is remove the 24x14 and add 2 smaller registers?