It's been a long time coming, but we finally have no doubt the model I've been calling Brawny is indeed John Chapman.
Cambria went straight to the source and contacted the Bob Mizer Foundation (BMF) for an ID. He tells me they responded to his inquiry within three hours and sent him the contact sheet below as proof. They also confirmed John did one solo film in 1969 that was never released. And get this! The source at BMF told Cambria they are working on gathering many of Mizer's films that were never released for a special DVD issue. This is exciting news! I suspect many of those films would include models from the mid to late 1960s that I've come to appreciate -- but the fact the mode!s wore pouches reduced their chances of being released after Mizer went full nude. This begs the question "Why was Mr. Chapman's film never released"? Beats me! Properly promoted I think that film would have been a good seller!
So thanks to Cambria for getting the name and the news! Great job mate!
P.S. It appears there might be a few more photos of John I've never seen. The photos with the goat and especially the one labeled BL would be nice additions to the collection. The search continues.