I’d guess Mandingo was EASILY 6.5” girth. Mine’s 6.3”, and his is visibly thicker.
But again, we’re getting sidetracked by talking about the dudes who far, far out there on the long tail (pun intended), which is irrelevant to the topic at hand. Isn’t the consensus that you’re “well endowed” if most women* (who’ve seen a penis or two in their time) would consider you noticeably bigger than average? So really that’s going to start around 7” or even 6.5”.
*and/or men, if that’s how you swing