If you look at his penis, you can see deformaties in the form of lines the type you would get if your penis was strangled and deformed by wearing cockrings. Hence it is obvious the method he has used, so i believe he has used clamping and hanged weights off at the same time, so that is erect hanging whilst clamped, which explains the expressive length gains he has enjoyed and the concentric marks of deformation. Its quite a dangerous method, but i guess with risk comes reward, im not advising anyone to try this and everyone has responsibility for their own selves, i merely highlight the method he may have used in my opinion.
I will never wish to get a penis length like that of mandingo. In almost all his videos, he was never able to go balls deep on the ladies. So what's the need of that length if you can't put all of it inside her?
Y'all should try out your dicks as you gain so you don't gain excessive unusable length.