I have a Carrier CNRVP042 evap coil and a 58CVA090-16 furnace and they don't physically match up. The coil is about 3" wider than the furnace. The installation instructions say to provide a field fabricated sheet-metal blank-off plate. Neither me nor my installer like this idea as it seems cheap and are worried about the blank-off plate sweating. Is there a better way to do this? I can't believe the factory would expect you to field fab a blank-off plate. This is for an upflow installation.