Here are the Wintec gullets. The blue is the medium-wide and the black is the medium. I had been riding Scout in the medium, but his back tracings and measurements were medium-wide. No wonder he was testy under saddle. He was getting pinched in the shoulders! (Thanks for alerting me to that Ms. Nancy!)
(It is really hard to tell the difference in the medium and medium-wide gullets from these pictures, but I wanted to post them anyway.)
Below photos are of the medium tree:
The photos below are with the medium-wide gullet:
And medium-wide gullet with saddle pad:
With the medium-wide gullet, the saddle sits a little lower in the pommel. This saddle is a 15 3/4 inch, and it still dwarfs Scout! It is definitely a better fit for me though. I believe I need a 16 inch in something...
Scout was definitely better under saddle today, so I look forward to riding him in the medium-wide to see if it helps relieve his fussiness.