Gas Forge Layout Opinions in Gas Forges Posted August 19, 2020 Buzzkill, I apologize for not quite understanding. Would you mind typing out your calculations? I gave the over all dimensions of the cylinder I'm using, so if with 2 layers of wool and one 1/2" layer of castable I should be in the ballpark of a 10"Diameter x 9"or10" OAL cylinder I think, which is what I based my calculations on in my previous comment. It's totally possible that I'm off on that so if you don't mind sharing why your calculation is so much different than mine? I am all for frugality, I can't imagine I'll be doing anything larger than the 8"x3" door in the back of it (will be the same size on the front), so given there should be a little bit of a lip to retain the fire I am okay getting as close to that as possible/need be. I already need to order more wool so doing a 3rd layer would not be a big deal.