I will have to check that out, thank you for the tip. I had thought that perhaps I could heat up the oven with the rocket, but I got my brain in a pretzel trying to figure out the damper.
I am adding aluminum foil plus 4 inches of perlite/clay slip as the base, then placing fire brick on top of that. E&E recommend, when a combustible base, 3 inch perlite/clay slip, I padded up. all that rests on corrugated aluminum. That should be enough for the cob oven, no?
The slab under the oven is pretty much all urbanite bricks from an old BBQ, stacked, packed and mortared together. I have some tile I was going to use for the inside flooring.
I am also worried about the RMH under the structure. One I don't have that much space, since I tossed the idea for a RMH being the pre/main heater. Two, if I end up making a small RMH, it may not even heat the bench...