After a week of sitting in the shop, it was time for a full on burn.
No leaks, and very good draft. 6 inch pipe thruout the build. The one thing I did differently is too make the entrance to the burn tunnel .5 of an inch smaller in one direction. That increases the draft in that area, and I can now load up the burn chamber as full as it will go, and I have no smoke back or back burn issues at all (so far).
I also find, that the 4 or 5 feet of bare chimney pipe is losing almost as much heat as the mass was absorbing. I know that I cannot tell what the inner temperature is on the stove pipe, since it now gets hot enough to melt the regular stove thermometer I was using, but the new chimney thermometer I picked up, is telling me that it does not get over 200 F . I do notice a difference at the top of the chimney outside, as there is no smoke, no steam, nothing to see - as if the stove is not even running.
On the plus side, with that large slab of concrete covering the manifold, my coffee stays hot ...