Oval Pompaii Igloo oven on earth bag structure

[Rich B]

Hi
Im building an oval Pompaii Igloo oven : 24" x 42" inside clear.
Any words of wisdom as I embark? I think Ill use foam forms or 3 of the
Irreplaceable tools to keep track of the radii. I plan to use the recommended
ht @ 20" & door criteria of an average between the 36" & 42" dome igloo designs. Chimney vent to be brick built 3" x 14"- is there any engineering #'s, rules of thumb etc for chimney calks other than 3x door ht?
I'm guessing that the oval dome will perform better than a vault, not as good as a round dome- any experience w/ a masonry oval dome to give me advice as to what some difficulties or pitfalls I may need to consider?
The oval shape is a product of available room and final design.


I'm planning on using Muddox fire brick-- only 26% alumina though-
Any better production firebrick for the price ±$1.08 ea, commonly carried by
masonry supply houses?

Thanks,
Rich