CB3000 Paired with a 6000s Cage?

Hi there! I picked up a CB3000 for my boyfriend. At first, he wasn’t keen on it, but now he’s warming to the concept and getting more into it. One evening when he went out, I had him wear it. When he returned, heading to the bathroom, I surprised him by going in with the key. I discovered that while his member is soft, he can actually pull it out of the cage and do what he needs. This makes me wonder if I should get a CB6000s for a tighter fit? Can the 6000s work alongside our existing CB3000?