I think D.Fogg's design would be good for damascus as the excess flux would drop out the bottom intead of into your refrac.
I have a 8" dia. pipe 11" long with 2" of kaowool and a waterglass coating on the kaowool.
It is built like raker's but with a ron reil type burner, about 4" from the back on a tangent and angled toward the front of the forge. I get forging temp. very quickly, Haven't tried welding in it.
My box fan makes more noise than the forge.
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Sola Fide