Rocket mass heaters?

Does anyone know anything about the claims about rocket mass heaters? (See this online tutorial here or the wiki page here.)

I would like to fit one of these into an Arctic cabin to replace a shitty pot bellied stove.

I am particularly interested in the claimed efficiency of these rocket mass heaters. If they are so much more efficient at creating heat from wood as compared to conventional stoves, they would certainly be very useful here as wood is hard to come by.

I’ve heard of these, and similar heating techniques. Without a large thermal mass they are probably not as efficient as claimed. They might work well with any other burnable material available. Pot belly stoves are probably not very efficient, most of the heat probably goes out the chimney.