CB Range discussion

I’m just getting started with wearing a chastity device and currently using the CB-6000S. Overall, it feels quite comfortable, and I can handle night erections well enough. My testicles are on the larger side but sit close to my body. However, after about 5 or 6 days of wear, they tend to retract inward, which makes the device slip off. I tried switching to a smaller cock ring for this issue, but it was too tight, and my testicles still retracted. Has anyone else dealt with this? Any advice would be appreciated.