Here is a place to start, possibly :
How I build my clips!
Hi everybody, After my last post I was asked how I made my clips. So I made a description of what I was doing. Have fun! Gregorwww.penturners.org
I know that you said you are concerned with how to construct the cap to receive the Fold Over clip, but I am not sure what that means.
Another option is to make the ring of the clip a bit larger than the diameter of the cap with the edge rounded and just let it show as a bit of bling.
If your tolerances are close enough and you use a thread sealant or locker of some sort, you won't need to worry about the clip spinning.
Bill
How to make the slot in the cap where the end of the clip is inserted.