Rocket Mass Heater Build

Hello everyone, I’ve been a lurker on and off for years. As you know it’s getting colder outside. In Maine it’s already down to the lower twenties and it’s cold in the house unless we crank up the Kineo cook stove. I made a wood box out of brick years ago when I built this house as seen in the pics. I need to make a heater  and would like to make a 6” rocket. I would like to incorporate the would box if possible. The wood mix is 28.5”L x 16.5”D x 27.5H. To the right of the wood box I have 64”L x 33”D of floor space and the chimney is centered on the 64” wall 2” of the brick wall. Money is very limited. We do have an abundance of beautiful grey Maine clay on our property as seen in one of the pics. We have a few good barrels with half to to 3/4 paint already gone.
For the heat riser I have 2@ 48” x 42” 18ga steal sheets I can make an insulated heat riser with using clay and perlite. The ceiling over the wood box is 102”from the floor.

Does anyone have any ideas or insight on instructing us on a way forward? Use the brick wood box or not use it and just do a small conventional system and save the wood box for wood. Time is of the essence and this is a project that that we would start right away and get done quickly as in we would work on it all day everyday till it’s finished. Thank you in advance!