hello all i really appreciate all the free advice and help learnining all i have recently about rmh i have devoted considerable time to watching videos and researching old and new tech relatrd to this subject since i accidently discovered mass heaters and rocket stoves about a month ago i have spent almost every free min i get to researching them i have for a long time heated my house with a super conventional "earth stove" witch i love but i see the awesomeness that could be with rmh tech my plan is to have my own when winter hits next year my big 2 qustions among others are 1. exact relationship of barrel and riser height . 2. what do you think of using a discarded fuel oil tank of about the standard 250 gallon home style as the base for a sort of portable rmh , build the j tube inside on a bed of sand cob around fill with gravel cut top front quarter off tank use rear top quarter as "barrel" some heat exchanger tubes run thrue foced air from my non used funace also cold air intake from said funace sucking heat from rmh and distributing it . anyway long time listener first time caller thanks for disregarding spelling and grammar flaws.