Steam main reduced

I just looked at a job where the boiler was moved from the middle of the building to the front of the building. The 1 steam main run's from the front to the rear, originally it was 2 1/2"  problem is that the guy who relocated the boiler extended the main to the front possibly about 8ft in 2". Therefore the main starts off in 2" and then increases to 2 1/2". I know this is totally wrong but I am trying to figure out the full consequences in doing this. I have laosh and I have all the charts to size the main properly, I'm just trying to figure out the full consequences of reducing the main where the guy did this. The house has a lot of uneven heat problems, though the main is vented with 1 Gorton No: 2 and the boiler water is clean and neutral.I am really just trying to figure out how much of the problem I will solve by putting the main back to its original size. The combined 2" & 2 1/2" main is approximately 35ft long.