experienced rocket stove advice needed!!

So, I have built a mock up outside which is not airtight at all but seems to work really well! my questions/problems are when i try loading fuel down into the chamber, i do not get as good of results as when i load it from the front with an air channel below the fuel feed. would this change once it is airtight and inside? i really want to use a clean out tee for the fire chamber, is this possible? I would like to dig a pit and insulate around the burn chamber with vermiculite so the barrel is flush with the ground, is this possible? any help greatly appreciated!!!