Found another Tom Morrison stretch that I like. Hits the lats nicely - sometimes I feel like it loosens my lats more, compared to the ring stretches, even though the stretch is not as intense. Well suited for practicing on breaks during your work day, because you can do it anywhere there's a wall.
I was wondering how long the stretches should be held as different schools advise different times - GMB likes 25-30 second holds, Mark Wildman says you should do at least 120 seconds, etc. Found the answer - from Tom's perspective - here. I like the simplicity of "until you feel a difference". I'm treating "difference" as any increase in ROM/looseness, even if it's very slight.