90 degree gullet currently with his fat pads.I had a pony about his size I think, she was 13.2 there abouts. She was wider (medium wide to wide gullet) but had pretty good withers. Is your guy built that way? I had an awful time finding a saddle, too. What fit her like a glove was an older Stubben. It was not a Siegfreid, but a very similar style. The panels had enough of an upsweep so they didn't interfere with her short back and it accommodated the rest of her nicely.
Every time I see you post pictures, it makes me wish I still had a pony to ride.