Is a Nano or Nub Better for the Holy Trainer?

I’m relatively fresh to the world of chastity and currently using a Holy Trainer V4 standard model, though it feels slightly oversized when I am at my most flaccid state. My wife often teases me while I have it on, which definitely causes an erection that pushes back against me with some pulling sensation.

I’ve also noticed that wearing it throughout the workday makes it feel quite loose by evening time; if I simply pull the cage away from my body, it feels like my penis might slip out of the tube. The 45mm ring is fairly tight overall and a bit difficult to put on as it currently stands. Do you believe opting for either a nano or nub model would tighten things up and provide more security? I am undecided between those two options. Has anyone here used both?