Clay cover on heat rizer 30 gallon cover?

Hi my name is Mikael Long I live in Asheville NC. I have been working on a MRS for the last few weeks I think I got a good model but made some changes in design and was looking for feedback. I will attach a PDF of the MRS which has the cover over the riser both covered in about 2 inches of clay mud and also topped with a marble slab that is about 1.5in and just bigger than the 30gl drum which is the cover for the riser. I used firebrick and used mud to make it stick together. I have about a 6in square burn and a 6in round exit, and exhaust. I have gotten good burns. I use wood pellets and a sort of Pchannel that is a Metal great that is shaped like and M side ways. This allows me to fill the back with pellets and get good airflow. It is also a more predictable burn cycle and has almost no blow back from say sappy pine pops or wet wood. The pellets are very low on waste and I believe they produce the most heat, but I do not know. My question is if the mud cover on the 30-gallon riser cover and the marble slab over the top are retarding the burn by not allowing the metal to cool fast enough or if the insulation simple keeps it running at a more consistent but slightly lower temp. I can just put my hand on either the top or the side but just for a quick second. The seat gets warm but not hot and the rest seems to do what it is supposed to. I get a great rocket sound and a clear sideways burn; I just have never seen one and am just going on what I read. I made several prototypes, including mini rocket stove and a small RMS (rocket mass stove is that the acronym).

ML,
Welcome!
I've never posted a photo so better ask somebody else but I would like to see photos of your RMH when you figure it out.
John

Got it see more pics in other posts.