Well the build is underway. I ended up having the foundation laid out and poured by a concrete company along with a pad to park my van and some repair of the driveway. It turned out to be a good choice as there was no way I could have physically handled the task or have done nearly as good a job. I decided to take advice received in a previous thread and filled in the walls with additional cinderblock topped by 4 layers of cement board. I used surface bonding cement on the inside surface of the outer wall and plan to to the same to the outside once the angle iron is placed to span the front opening (every 8"). The angle iron had to be ordered and should be delivered tomorrow. Once the hearth is finished, I expect to be asking for lots of advice as I set out the final layout and actually begin work on the dome. Thanks again for all your help so far. I am attaching a few pics of my work so far.