Yeah, I'm inclined to think that the source of the vaginal skin is less important than the personal issues of anatomy. I do know that Brassard advertises that he removes an approximately inch-square flap of skin from the perineum, which is where he places the vagina for most people - meaning, essentially, that it's possible to conclude both that a) the perineum is smaller afterward and b) that the vagina must be typically located in the inch of perineum farthest from the anus (because it would illogical and dangerous to place the vagina as close to the rectum as possible). This is true for me; I definitely have less perineum now, and my vagina is placed so that the "top" edge is more or less where the very end of my scrotum connected to my body. Based on my wife and what I have seen of cis porn, this is well within accepted variations - nobody should be down there measuring to the millimeter, after all.
The only real difference I notice is that the angle of my vagina is a bit steeper - towards my belly button - than my wife's. But again, I doubt anyone who's not obsessive about it would pick up on this, and it's still within the cis range. My vulva does extend a bit higher up my body that my wife's, in that a little more vulva is visible standing with legs closed than on her, but I've seen other women where that's true, so I have no real idea whether it's her or me who's less typical.
The vagina itself is NOT placed where the penis appears to connect to the body at the pubic mound; that *would* be ridiculously anatomically inaccurate. In reality, the penis "root" extends quite a distance into the body under the skin, and that's what's being built on when it's inverted, as I understand it. I don't even have a scar where my penis appeared to connect at the pubic arch, and I have no explanation for that part...
