Very true, Tammie. Technically no guy on earth would be *too* thick. The average circumference of a baby's head is 13.5in (13.5 inches "around"). However, keep in mind the onset of labor involves a variety of hormonal centers to deal with the trauma. Things like oxytocin, endorphins (beta-endorphin), epinephrine and norepinephrine.
Some people will know that these are also increased during sex or hugging (oxytocin can rise in the body when you hug or touch). The thing is the levels are astronomically higher in labor. This is how women survive the trauma. Some women even report a feeling of calm or ecstasy. This is b/c of things like the high levels of Oxytocin ("love" hormone), or the high level of beta-endorphins (our natural opioid and pain killing hormone which rises dramatically in labor). The same can be said of the adrenaline family too. That's where the term "Runner's High" comes from. It's not exclusive to running (it can be any exercise) but the term got coined for runners. It's because their body is producing adrenaline family hormones & endorphins. These can make a person feel "high" (or at least "ok" during a painful event - like, say, a 26 mile marathon, or.... child labor).
Anyway, point being women can obviously stretch to 13-15+in of girth during child delivery. Circumference not diameter (i.e. width).
Circumference is equal to: 2R*pi where R = radius OR D*pi where D = diameter (where R = radius and D = diameter)
So, max width is about: D/pi = C (where C = circumference)
Substituting values: 14/3.14159 = 4.456in
Max vaginal stretch in terms of width: ~4.5 to 5 inches +/- .25in to account for small/large babies
(frequently involves tearing/bleeding - the perineum area in particular)
That basically means no man on earth is too large... haha. Because no man is 4+ inches across (width). The largest known is estimated at 7.5EG (only one man thought to be even near this large). That's roughly 2.466in across.
BUT, keep in mind that sex is very different than labor. The woman will not have those massive levels of Oxytocin, endorphins for pain killing, adrenaline...
That's why I say my hypothesis is that anything approaching 2.5in across (which would be over 7.5in EG) is getting absurdly wide and would be painful for almost any woman.
It's a good thing that virtually no man, at least none we know about, is beyond that range. That's so insanely rare that if you were even 7in EG you are in a group so rare it's at least 99.99999% (1 in 10 million).
Even at 6.25in EG at the base (and ~5.9-6in at *very* tip) it's not always easy if the girl is not ready. I've had girls tear with vigorous sex or frequent daily sex or too many hours. She might be bleeding, certainly the next morning she is usually very chafed, and you may have to wait a solid 2-3 days before hard sex again. No, not always. Depends on her hormones, her lubrication, her relaxation, excitement, and so on. But, yea, it happens even at that range (~1.9-2 inches wide). It's not like a major issue but it is big enough that condoms hurt, some flat out don't fit, definitely won't roll to the bottom, sometimes you have to hold it (lol I remember some of those occasions) so it doesn't slip off b/c it wouldn't roll past the first third. 7in EG though? Holy shit.
It's all gonna be dependent on the girl of course. Her hormones on that day, her lubrication, excitement and everything I've said before. But, generally speaking, over 2.15 inches (around 6.75in EG) is gonna be heading into rare monster territory. Beyond 7in EG is just unbelievably crazy. You basically will have to order custom condoms and I don't even know that anyone makes them large enough for that size. It's hard enough even at ~2in wide like I said. Something up anywhere close to 7in EG is a friggin monster. I mean a goddamn monster.