I can only speak from my own experience. I was small when we started and I'm a grower as well. When fully erect 12 years ago, I measured about 4.5" inches and when flaccid, I was about 2" and thin. Since starting, 12 years ago I have had these observations:
I started with a plastic cage as there was not as many options as there are today, and it had a variety of rings to try. I soon learned that plastic is not very comfortable or hygienic. Stainless or nylon seems to be the best.
After some research, I learned that morning wood was painful due to the ability for your penis to grow in the cage. Prevent it from starting from growing, then your penis learns that it won't be able to grow or become erect and in a couple of months, it becomes much better for you when a cage is snug rather than too big. Smaller is much better for long term use. Counter intuitive I know.
About once a year, I got a new cage/styles and each year I discovered that my penis was a bit smaller in its flaccid state each time I measured for a new cage. So I went from a 3" cage to my current 1" cage, again over 12 years. Usually smaller by about 1/4" a year.
Once a few years ago I had to travel a lot and the hassle with TSA just made wearing a cage a hassle, so I had a 3-month break. What I learned is that, yes it did recover by about a half inch, but I could not get fully hard.
My final take is that if you want to shrink your penis, chastity can do that - but it takes time. As mentioned in an earlier post, using a system that gets smaller and smaller gives you the best path forward.
One observation is that the skin on my shaft is now slack since the penis itself has shrunk. So wifey is planning on a second circumcision to tidy up the loose skin by getting a high and tight cut.
I'm not sold on the flat cages as it pushes everything inside and perhaps for play that may be fine, but full time - skeptical.
I can get a ruined orgasm via prostate stimulation, so I do get that about once a quarter.
All I can say is that my penis is envious of my tongue - it is now my main sex organ.
