You'll find tons of current and evolving info re: Rocket Mass Heaters
in the following forum :
http://donkey32.proboards104.com/index.cgi#test
You will find a growing number of people internationally who're
actively working on getting rocket heaters up and working, as well as
experimenting on other designs, to see what works best for them.
I've found the RH Forum incredibly helpful and pro-active !!
Consider joining that forum and contributing !!