Thanks for the very detailed explanation and for welcoming me to this fantastic site. It would appear to me that a dual rocket stove system may be more beneficial as the 20' limitation may lead to cold spots which will affect the overall heat of the structure I think. Perhaps if I were to place the two stoves in the middle and run the exhaust for one left and the other right, I could build the fires at the same time and at the same location, this would spread the heat further into the overall mass and lessen the cold spots in the mobile home. Luckily this mobile home already has the duct work removed from a previous owner when they replaced the flooring so that's one challenge out of the way. I will definately under the mass with bricks and a moisture barrier which will also lessen the need for the amount of cob material to pack under it. I have never built this type of stove before but I see it's benefit and I will definately post how this build goes and how well it works after it is complete. I will have to wait until spring to start on the project but doing the homework now will make it easier. I think for others with a mobile home this would solve a few issues such as the ones I already have. My mobile home is an older 1970 model which is unable to be insured as a mobile home due to it's age, however with a solid foundation underneath, it now becomes a home and not a "mobile home" which makes it insurable. The other issue this will help with is that I can use the cob material as the underpinning which will prevent those cold air leaks associated with mobile homes. Not to mention it will prevent the critters that seem to make their way easily into mobile homes. I wonder if it would be possilbe to run a coil from the cold water inlet to the hot water tank into the cob material below and then back to the top of the hot water heater with back flow preventer, this could potentially preheat to a certain temp the water prior to entering the water heater. OK I'm rambling but again thank you so much for the information and I will do my best to post here how the build goes.