As usual, Stone Andy, I think your posts are insightful, sensitive, and well articulated.Here is something I haven't seen discussed on this topic. I'm 75, and until about 8 - 9 years ago my erect penis was straight as a stick. However, I suddenly noticed curvature due to Peyronie's disease, which is caused by a weakening of an internal penile structure. My case is mild, but the curvature has shortened my erections by about 1 " . No difference in the quality or longevity of the erection, just the length. It was very disconcerting at first, but I've come to accept it and appreciate that no functioning has changed, just appearance.
It hasn't shortened your erections as much as you now need to measure the outside curve and inside curve and average the two for the most accurate erect length because the two are now significantly different whereas before they were almost exactly the same. And a curve means you have to use a string laid skin tight along the whole length and mark off the tip and then measure that length to get the accurate measurements.
I was never that big but I know I was 6 inches in my 20s and 30s. I stopped measuring after that until I was in my late 40s and had gained a lot of weight (from 189 to 240). I'm down to 221 now but there's still some fatty tissue around the base of my penis and unless I push the ruler firmly against the base, it only measures slightly over 5 inches. I've also noticed that when flaccid, it shrinks down as much as 1 1/2 inches. 20+ years ago it would be about 3 inches flaccid.
After prostate radiation for cancer and hormone therapy in 2020, I noticed a real decrease in both penis and testicles size. Once I was finished with the hormones, my size began to return. My penis is now thicker than before but decreased in length from 19cm to 17.5 erect and my testicles seem even larger than before. My urologist prescribed a daily 5 mg of tadalafil which causes me to be plump much of the time. I try to maintain masturbation twice a week. As I approach 80, I miss the old days of erect at will and large discharges but feel grateful for my current ability.