I've never turned down anyone for being too big. With proper foreplay I don't think there is any natural penis that any woman on earth can't accommodate vaginally. When men say "it didn't fit" (vaginally) they're either bragging or they need to work on their foreplay skills
Anal is a totally different matter. Several of my friends have told guys they were too large for anal, but keep in mind that in many cases this is just a way women say no to anal while still stroking a guy's ego
I'm up for any challenge as long as it's
natural. Some of the pumped/silicone injected cocks I've seen made me cringe
Although I agree, generally, I think there are conditions that would render some incompatible. Like you say, "i couldn't get it in" stories are rarely a result of the actual size of the genetalia, but I do believe some physical and mental issues could prevent a comfortable fit.
Which brings us to: yes it may actually go in, but at what cost in comfort or even pain? I say it doesn't fit if you give it your all and it just hurts; even though it did, technically, "fit" inside. And what do we consider reasonable? Surely there are medical conditions that would disallow.
Don't get me wrong, I think 99.9% will fit, and the .1% that doesn't may be due to a "condition," if you will, but I think we have to accept that there are always exceptions.
Personal experience is relatively moot, but I would guarantee (dubiously, of course) that every vagina I've been with could take a very large(r than mine) penis. Maybe not all the length, but 7" girth seems like it would be doable for even the more petite vaginas I've known.