2 1/2 to coil on the inside work with a 3 ton condenser on the outside

It used to be the set was matched or a coil was 1/2 ton larger. 3 ton coil and a 21/2 ton condenser. With the newer Freons, larger linesets and valving not sure how mismatched things can be. I would consider a lower coil BTU to be worse than a lower condenser BTU.

You really do not want to do that. Get the correct size or one a bit larger.

One of the reasons you use a larger coil is that it has more surface area not just to cool but also to dehumidify.