I've never talked inches (or centimeters) with any of them but I've shagged a fair few cock-wranglers and none of them ever complained about my utterly average knob (or even slagged me off as being small-knobbed during any one of a zillion heated slanging matches). Honestly, once you've bedded 4-5 30+ cock whores and they all love your average knob life gets a lot easier.
Sorry if none of this makes sense lads, I'm pissed to fuck la.
Honestly I think that it's mainly just that (at least in my experience) women tend to care a lot less about genital aesthetics (size, shape, and so on) than men do. One lass I'd been seeing for at least a couple of months had absolutely no idea I was circumcised despite having had my penis in her mouth dozens and dozens of times. Her excuse? "I just didn't really pay that much attention". Well, thanks for that?
While I could probably build a 100% accurate full colour 3D model of every vagina I've ever been in contact with most lasses seem to lump knobs into three rough categories: Micropenis, Ouch, and Everything Else. What this means is that I think most lasses probably aren't shagging away thinking "yeah this guy is definitely packing half an inch less than that other lad", probably can't tell the difference in an inch or two anyway, and if your old chap doesn't fit into the Micropenis or Ouch categories then it's probably entirely forgettable, just another faceless shaft on the cock carousel.
Either that or I've just been hanging out on the wrong side of the tracks all my life.