Greg, I haven't had any puffbacks, as you note the design really helps with that. My issue was being accustomed to burning well seasoned hardwood that responded to loading much more quickly than coal. That and taking eveyones advice to heart about running too fast creating clinkers and not giving the WM design enough credit for preventing backpuffs contributed to my frustration. I've developed a reasonably good "System" for reloading now, I have the BD dialed in to suit me, and I'm much happier with the stove. I still sorely miss the bimetal, and really need the extra capacity of the 400 to extend my productive time between loads, but I'm much happier now.
I sincerely appreciate everyones help. Without ya'll I would never have made the WM work.
ETA: JohnHenry, you have a PM.