If the 2 ton Carrier unit easily cooled the house, what was the reason for increasing the size to 2.5 ton?

I have never heard of the Federal Law on 5 year freon warranty leaks. What exactly does the 10-year limited warranty cover?

If you have a leak, then the contractor repair it? Do you inspect your duct work? Perhaps a flexible duct has fallen. This may explain the temperature drop issue.

You filter is a little small for a 2.5 ton unit, but I don't think it would be causing any of the problems you are describing.

Is the contractor coming back to fix the problems?

Eddie, with your experience I won't go over the obvious things that could be causing the issue. It is possible you don't have a leak but still be low on refrigerant. Proper pressures don't just permit proper heat removal at the evaporator but also serve to keep the compressor cool and to keep the oil where it belongs. If your refrigerant charge was really low (as would an over charge), the unit could have pumped oil through the system. This would have decreased the inside diameter of the refrigeration circuit throughout the system. It would also act as an insulator to inhibit proper heat transfer. Once you charged the system, the oil worked it's way back to the compressor and now the inside diameter of the tubing is larger. If you check the charge, it may just need additional topping off. To do a good charge on a system, one should look at amperes, temperature differences between suction and high side lines as well as head and suction pressure. I personally also use an electronic sight glass to further help in a good and efficient charge. I'm not saying this is your exact problem because the expansion valve and fan speed can be the culprit too. But, I've trouble shot enough problem units through the years where what I described has been a factor.

I've also seen this happen on units where air has gotten into the system where the technician forgot to purge their lines. The moisture collects as ice at the metering device and then goes through a melting and blocking cycle that never allows the evaporator to completely do it's job. Also, an overcharge can cause it. As you know but I'll mention for the sake of those that don't...a refrigerant charge peaks out and plateaus. Adding more refrigerant then starts a drop in the cooling capacity as well as causing other damage like bent valves in a reciprocating compressor or damaged pistons.