I was not suggesting that the wood feed opening be outside of the building. I even suggested that a simple box could be made (that was plumed to the outside) sit over the wood fee when you were not loading it. I agree that running a superheated pipe through a wall is not the best idea and there would be potential loss of heat in doing so.
Lets say that the RMH is moving 50 CFM, so what you are saying (or I'm asking) is that you are pulling into the room that amount of really cold air, maybe below freezing into the room. Would we put a six inch hole in the wall, to the outdoors and turn on a small fan in the middle of winter when we are trying to heat the same room? No, but that is what is happening, through all the small leaks, you just don't feel it like a small blast of cold air coming off a fan.
I think that the warm air going into the RMH, is not required (I don't remember all my physics anymore but I think that wood burning is an exothermic reaction and the amount of heat given off is not affected, but the air being heated is going to be colder). I believe you might burn an insignificant amount of extra wood to make up for that small delta (to regain that amount of heat loss), but I don't think you could measure it.
My question was digging into maybe your last comment about the total length of the entire duct system. So is the rule of thumb, that it take into consideration the entire duct length, both pre & post burn into your total length? I have not seen that restriction/dimension in the forum so far. What is that rule, or is it trial and error, base on the size of the fire box, chimney size/length, reburn chamber, exhaust duct dia..... etc? My guess would be to increase duct size to reduce the pressure that slows down air flow if you need to go longer, but I'm sure there is an upper limit that makes it to bulky or worth the effort.
Maybe it was something that you guys have not gotten around to yet or no one thought about it yet, but it was curios to me not to consider it. I have a couple of other ideas around the bench, the heat chamber and a few others....