Probably best to read this
http://www.fornobravo.com/forum/f28/...rill-2207.html (Casting Refractory - This is NOT a drill!)
and then ask ENZ since he is the only one I have seen do it. Now, I did cast my vent transition and a dome plug (approx 15" in dia and 3" thick). The material I used (KS-4) has held up great and am not worried about cracking at all, but it required a specific heat cure schedule. So you could not use it unless you cast pieces small enough to fit in an oven or had a friend with a very large oven/kiln.