I have a customer who has a furnace that is grossly oversized. Her furnace is only about 3-5 years old and she can't afford to replace it again. I have done a heat loss for her and it comes in about 45,000 btu's. The furnace she has is 80,000 btus and is an extremely small house. I am changing the ducting over for her. That was wrong also. Has anyone ever downsized a furnace by blanking off orifices, say opposite the end of the ingition system? Would you consider this an option or am I thinking way out of whack? I am wondering if there will be any kind of problems later or if it will affect the heat exchanger in some adverse way. I am not sure I am going to do it, but thought I would see what you guys think. Maybe just plain nuts for thinking about it.