You mentioned he's a "teddy bear". Is it possible that his sit bones are wider than the average guy's, and so instead of sitting on the suspended leather portion of his An-Atomica, he's sitting on the metal frame the leather is tacked to instead, or too close to the frame? (which would be VERY uncomfy on the sitz.) I think MimiTabby or someone said the An-Atomicas come in 3 different sizes. Maybe he just needs to switch for a wider size?

Somewhere there is a thread with a jillion very cool ideas for how to measure sit bones. (you just want to make sure his saddle is a good 1-2 cm wider on each side than he is, so 2-4 cm wider total to avoid the metal frame and to be sure he has wiggle room to shift positions)