Switching from a CB6000

I’m sharing my question from the key holders section here. They haven’t offered much advice there, so I thought posting it here might help. Hello everyone, I’d appreciate your input on a choice I need to make. My husband is fairly large when erect, about 8 inches firm, though he looks smaller in his natural state. I began using him with the CB6000 roughly twelve years ago and he fit it well back then; no trouble standing up to urinate. The situation has shifted now because he shrinks more at rest, so I switched him to a CB6000S to ensure the head reached the end of the tube. After five years in that model, he doesn’t quite reach the end anymore and must sit down to pee. He remains around 8 inches when aroused, which suggests this shrinking is just part of aging rather than an issue with his size during use. I’d like to put him into a smaller cage now. The Holy Trainer V5 looks appealing. The ring fit isn’t worrying; he wears the 50mm ring on the CB comfortably, so that should work fine for the HT as well. The real question is which tube length to choose. Has anyone here made this switch and can offer guidance? Thank you all.