I have just recently been interested in learning how to make a roacket mass heater and was wondering with a big enough system could there be 2 warming benches in 2 directions and if so will it hurt the draft to have 2 vents i plan on practicing out doors with a hot tub, sauna and if im sucessfull i was thinking of making a home heater as well currently run off an ashley wood stove burn about 6 cord of wood per season heating a 1965 trailer with full lenght addition. i would also like to say i love your site and the things you are doing this is so awesome and interesting i wish i had discoverd this 10 years ago and again thank you for your input. joe in maine