There is no real data on this that I’ve been able to find. All anyone can go on is experience.
I knew a kgirl who called unusually large dicks “porn dicks”. From her description I gathered this was anything from about 8 inches up. I never got a good idea of what kgirls considered too girthy. There was both a lot of variation and exaggeration. So I gave up trying to figure that out. Maybe someone else has done a better job of figuring out kgirl girth limitations.
From my own experience prior to when I started to look specifically for girls who were magnum friendly, my odds with kgirls were in the neighborhood of 1 out of 3 failures. A failure consisted of anything from an unsatisfying session playing dodge the pickle (one of my least favorite games) to outright walks. By walks, I mean where the girl said “honey, too big” and gave me my money back. Or in some cases said “blowjob only” and gave me a significant discount.
From talking to girls and playing far too many games of dodge the pickle, I’d say that you have the best chances of a good experience with a kgirl if you are 6.5 inches or shorter. I’m guessing, but I’d bet that 6 inches would be the sweet spot compromise between enough length to get a really good stroke and not being too big for the majority of kgirls.
As put by one of the kgirls I’ve known, anything above 6 inches makes for a “good boyfriend, bad customer”. And I’m not sure she really meant the “good boyfriend” part.
The net is that kgirls who actually like porn dick are not common. And anything over 6.5 inches is too big for many of them.