I'm a huge fan of the site and your research (going back to the beginning). It's great stuff. I'm particularly happy to see that you have updated your scarcity charts, and that you have taken into account high value bias. It is a really smart idea "that reported condition profiles for T206 subjects in the PSA Population Report are different due to high value transaction bias." And that you can derive useful information from the fact that more low grade Cobbs get submitted for grading than low grade Unglaubs.
I know you have Doyle throwing as theoretically on the scarce side. And I get it - it's a Series 150 only subject. But, my experience has been that this card is not so tough. Anecdotally, of all of the signed T206 cards that found their way onto ebay in 2007 from The Great Pittsburgh Find of Signed T206 cards, the most prevalent card was a signed Doyle throwing (5 examples). And, even if you assume it's because Doyle was an easy signature at the time, then isn't it surprising that only 3 portrait and 2 batting poses were signed?
Obviously that's just one universe, but in my two runs up the Monster Mountain I have not found Doyle Throwing to be particularly tough either. I can't see how SLer Ed Foster could be found even slightly more easily, as your report suggests. Theilman, who you rank alongside Doyle, is way harder, in my humble - non-data driven - gut feeling/opinion.
Regardless, very very helpful! Great stuff!