Thank you Matt, I believe I understand your points...
I also believe that I'm going to take this little 15# tub back tomorrow and exchange for the 50# bag, it just seems like such a better deal.
I'm going to start scouting local free clay. I grew up near a ravine and I remember a location where a street storm drain spilled onto the side of the hill where we used to dig the clay with our hands and make goofy sculptures as kids would... My old stomping grounds is about 15 miles away and I think I'm going to take a drive this weekend.
I'm also close to acquiring a garbage can of free powdered ball diamond clay! That might happen this weekend! ...fingers are crossed.....
What do you think about using a scuba tank the inside lining for a heat riser? It's nearly 8" in diameter but not quite so tall. I figured that I could cut the top and bottom off the tank, add some firebrick to the top of the hot side of the burn tunnel to build height, and then place the shell on top of the firebrick.