.. The chart clearly indicates that a 7 1/2 x 7 1/2 is at the perfect or excellent pleasure . We will see if the host attaches my chart that I downloaded from a research lab
I saw that chart years ago before I started PE. It shows a girth of 6 to 6.5” as being the preferred. I thought that was ridiculously big. Since then I have worked my way right through that region and am now well above it.
With my present partner 6 to 6.3” was the best sex. She is Caucasian and has had children but via Caesarian section. It was tight and I was long enough not to come out when thrusting but short enough not to hurt. It did take some 20 minutes or so foreplay for her to moisten and relax enough to take the girth without pain.
Once beyond 6.5” girth full penetrative sex became difficult and I had some bad experiences with my glans being inside but fitting too tight to ejaculate.
Other partners I had when younger varied somewhat. One single mother had a young child through normal birth was quite loose with my 5.3” girth. I expect she could have accommodated 6.5” girth easily.
So I agree with the the OP views - there can be a downside.
To add something not yet commented - once you are convinced PE is possible it can become addictive. It takes a while to establish a reliable and workable routine - knowing time and load give steady gains. To me it is very much like continuing puberty. From month-to-month I notice small changes down there. Pumping gives a short term indication of what it is like to be bigger then over time those gains become permanent. From year-to-year I need photos to remind me where I started. Just observing that my hand does not wrap around my cock increases the intensity when I masturbate - I can still shoot like a teenager but not as often.
So be aware it is possible to be too big for a particular partner. And there are issues with women ageing particular as they go through menstruation. So things can change over time. If you want to have normal penetrative sex then err on the undersize of what is pain free now. I cannot go back now so I have lost some of the enjoyment of sex with my partner. On the other hand I am still getting bigger as that is a turn on for me.