I can't tell you what's right but I can give some of the factors.

Depends on the size and weight of the ring. For me I like a smaller **p if the ring is heavy.

The size and width of your fingers. You may not want the **p to allow the ring to fall "through" a single finger (but I do).

If the edge is beveled the **p doesn't have to be as big. I personally like a beveled edge. It is easier on your hands.

If you are going to do spins in any direction you'll want a smaller **p.

If you want silence, bigger is better.

Most rings come a little small so start there and work a while. If it seems too restrictive make it a little bigger. Small, incremental changes are better.
I find it harder to close a **p that to open it so you don't want to go too far.

Buying some cheap Rings at a Club auction is a good way to bash up and make your mistakes without ruining your better set.
Just remember to do some practice with the good ones before a show.

-Mary Mowder

Regardless of how wide it is, if you want it wider you should actually cut some off and not try to "spring" or bend it wider.

--and I agree. I'm using 8" rings (1/4") with a 1/2" g--. I'm using the routine that Karrell Fox gave me in the '70s, and there are no "fancy" moves!

In my book The Real Secret of the Chinese Linking Rings Jay Marshall's Key Ring with two openings is explained.

I can't credit the originator but Bob Brown passed on the advice he'd heard.
Best advice I ever got about linking rings and my guilt about the **p was:

"You have to hold them somewhere".

Silly but it really helped me.

-Mary Mowder

My thinking is the **p should be whatever your routine requires and you can handle. But for me, I have found bigger is actually better for most moves and am guilty of grabbing a hacksaw as a remedy.