How many are running a coal fired heating appliance though? You don't need a lot of chimney for oil or gas as they are forced draft. The 2' at 10' is to keep the smoke away from the home, not for draft.
If you have a stoker it doesn't need quite as much draft as a hand fired. The absolute minimum for a hand fired is generally accepted as 20' from the appliance exhaust port. Because your chimney is going to be exposed to the cold I would reccomend the additional height. You could reduce it by insulating the flue as mentioned earlier in this thread, if I had the steam I would do both. As I said earlier, in a ranch you won't see the house competing with the chimney as bad as a two story will. But with any combustion byproducts it is best to err on the side of caution. The worst thing that could happen if the chimney is too tall is that your appliance will perform better, and that really isn't a problem. If you unit is on the first floor and is 4' to the exhaust from the floor and your first floor is 2' off the ground, your chimney is going to need to be about 8' higher than the peak. Cheating on your draft will give you poor performance no matter what the appliance is. And poor performance is not going to make you happy with the project. We are all about happy here.