I am going to build a stack stone outdoor fireplace in my backyard in the slower months. One of my employees has done it before, so it should be interesting. I wanted to see if the materials price was in line. The brand is Isokern. Here are the prices... Chimney box 36" -$1300/Chimney box 42" $1900... 3 stacks - $240..... fire brick- $145. Does the price on the Chimney box sound right? Do you guys do 36" or 42"??