5 ton unit on 4 ton ductwork? Duct work is sized for a 4 ton but Icontractor wants to put in a 5 ton condensor & evaporate coil unit to cool the house better. House is 2750 sq ft. The contractor thinks I really need a 5 ton unit instead of a 4 ton. The problem is that all the duct work is in the concrete slab and can't be expanded. I realize that the cfm for a 5 ton should be 2000. The cfm on the old duct work is 1600.

Will the 5 ton perform well in a 1600 cfm duct work system? Or will it NOT perform well in a 1600 cfm ductwork?

The return suppy is currently sized at 1950 cfm. It can be increased because it is in the attic.