Here's a view of the curvature of the base:
Here's are some views of the top of the stack:
It looks like the top of Betsy's stack was round and about 12" in diameter. The accident that knocked the stack off also ripped off the upper part of the stack. That part was not evident at the site...
Finally, looking at the front of the stack carefully, I noticed a chiseled "F" in the vertical part of the base flange to help shop workers properly orient the stack if it was removed:
That's all for now. I hope historians and modelers can use this information. I'll let the group know if the Forest Service allows its donation to a museum....