i am not sure what size should i go with.
the 15mm large size i find it kinda thick for an adult male -thats just how i see it.
what sizes do you use? mediu+small ? or just large?
is the large one ok ? or should i go small and medium?
I would just go large, he'll be able to climb it perfectly fine. Not to mention he shouldn't be able to clamp all the way around it regardless that will cause sores if he is on it enough. The larger one should be fine for an adult Male like the veiled you have.