Does that additional eighth of an inch truly make a difference?

I just got my hands on a CB6000, but I’m having some trouble with how it fits. I’ve experimented with the stocking technique, plenty of lubricant (both water-based and silicone), and inserting while completely flaccid. However, I often end up with that donut-shaped roll of skin behind where the penis enters the tube. It doesn’t feel like a length problem to me; rather, it seems girth-related. Because of this, I’m thinking about buying a CB-Curve cage. Has anyone else dealt with this? Does that extra 1/8” actually matter?