I have been a nudist for decades and take weekends and long vacations to clothing optional/nudist resorts and beaches, and for several decades I was in the "lifestyle" (read swinger) going to many "lifestyle conventions" that lasted anywhere from a long weekend to a two week period...usually held at clothing optional/nudist resorts/hotels. And as a nudist and when I was in the "lifestyle", and in just the serendipity of life I've encountered some other very extremely endowed men.
So far, only one fellow, while not "bigger" than I am (both length/girth for mass) in that his flaccid "beats" my erection, he is certainly longer flaccid than I am erect. But his is very thin flaccid, and hardly grows any when he becomes erect...his circumference when he is fully erect would be, at best, would be like a "small thin average" girth. He has two "wives" and I have, just by chance, encountered he and his "wives" a few times at a resort in Florida and a nude beach in Florida.
I have heard of one other guy but I have not seen or met him. It was quite a few years ago but I was attending a "lifestyle convention" at a clothing optional resort in the Caribbean, and I met another extremely endowed man and his wife. Both of them told me about the guys father, (wife's father in law) and how enormous he was both flaccid and erect in length. They both said I was thicker both flaccid and erect, but that the father/father in law was longer both flaccid and erect. The father and his son, from what they shared, were the same thickness flaccid and erect, but the father was longer both flaccid and erect than his son. The wife knew from experience because they told me that she had dated the father, now her father in law, before she met his son and married him. Given the endowment of the guy in the couple, and the obvious sincerity of the two of them, I have never had a reason to doubt what they told me.