The Corkscrews are all sized to match the Inner wear. As we have 99 sizes of Innerwear we also have 99 sizes of Corkscrew.
The Corkscrew actually has more latitude for sizing that the Innerwear. For a smaller lighter version that is easier to put on and conceal under clothing you can shorten it by cutting off one coil at a time with a box cutter till you find your preferred size. The kit comes with a PVC end cap to seal the wire.
I personally prefer mine two coils less than full size.
Of course the girth itself is easily adjusted by screwing or unscrewing the coils. If the size is very far off you can use a suitably sized cylinder to act as the forming tube.
You should have no problem to get a good fit with what you have now.
Let me know if you need any further assistance.