I have now changed from the 6000 to the s model and it is surprisingly comfortable! I was chatting to someone via fetlife who is very experienced with the nuts and bolts of chastity and he suggested it. I was expecting to feel more discomfort but as he explained the smaller the cage the less erection!
Hopefully I will become a Mature Metal customer in the near future as my wife is getting more and more into my chastity!