A decade or so long ago I won't tabulate it, I started some P.E.
To this day after I basically squashed my dick so hard it exploded in girth, it remains to this day.
My point is if you start young and go for another 4 or 5 years I'm sure some guys hit 10" or beyond by mangling the tissue, healing and repeating during puberty.
Now what guy can do that without his parents being all "wtf are you doing in there!??!" and disrupting progress?
Guys in 3rd world countries mostly.
My point is, I think you can stretch length and hyper inflate girth until your fun parts are just ridiculous but the odds of living in a culture where you are unbothered to achieve this are literally 3rd world or, a 1st world fatherless ghetto.
I reached about 7 and 7/8" when I'm in good shape and my girth can hit 6.5 to 7" because of that bout of "squashing" around 15. The bigger you get?
The easier it is to perform P.E.
So I don't think it's far fetched for some guy that's 5'6 to stretch and grind himself above 10" but take this as a warning.
With a woman my dick is hard as a diamond.
By myself I really have to focus and get lost in fantasy to achieve equivalent for several minutes.
If you mutilate your dick through P.E. techniques during puberty, you better for damn sure be into the woman you are with regularly if you expect to have a rock hard dick that pushes her into orgasmic euphoria assuming she can even withstand it!
At roughly 8" most women see what I have and go into a laughter of "omg wtf...." so beyond that majority are gonna run the fuck away man.
I think these guys at 10" and beyond exist but they've fucked up their bodies to a level that the only partners that can tolerate them are gay men. You are literally building a dick restricting you to being gay or at least, hanging 2-3" outside a woman making the excess utterly worthless.