I always go with the snake girth and I get the same diameter perches. Also adding a crossbar would help him.
Thanks! That's a handy perch sizing rule -- I'm surprised I haven't heard anything like that elsewhere. I'm looking at the perches at Specialty Enclosure Designs and will probably pick something up from there.
0.1 Sonoran Boa sigma: "Adelita" ('19 Hypo het. leopard)
1.0 Boa imperator longicauda: "Kuzco" ('19 het. anery)
0.1 West Papuan Morelia spilota: "Pandora" ('20)