Im going to replace my rheem modulating with a new Airease mod. Furnace this weekend. My current setup is single piped with 3"about 20' with a 2" termination through the wall. The venting is short so i can stick with 2" or should i do 3"? I guess my question is is larger better for a short run? Are there pro vs cons for short 3" runs? What would you do?