The mandingo videos may help with this. My results so far are:
----------------------------black --------------white
0" of penis showing--------2 chicks-------------1 chick
1" of penis showing--------5 chicks-------------3 chicks
2" of penis showing--------1 chick--------------1 chick
3" of penis showing--------0 chicks-------------3 chicks
The above averaged out:
So far the white chicks are taking him within slightly less than 2"
So far the black chicks are taking him within slightly less than 1".
I think Mandingo is stated as 11.75" (porn hype?) and I realise the topic of his length has been brought up before, but does anyone know if it has been determined what his length is? I'd like to know for sure how much dick these chicks are taking.
IF he is indeed 11.75", then for this thread the above chart can be read as:
vaginal capacity------black --------------white
11.75"+ ------------2 chicks-------------1 chick
10.75" -------------5 chicks-------------3 chicks
9.75" --------------1 chick--------------1 chick
8.75" --------------0 chicks-------------3 chicks
Averaged together maximum length can take:
Black women: slightly less than 11"
White women: 10"
You asked for universal. If by that you mean a penis that will fit in almost all women, but still be as big a penis as possible, then, in general, judging from that chart it will be just under 10" for black women and just under 9" for white women since those are the smallest vagina results on the chart. (I don't know about Asian women yet, but I suspect it will need to be under 8"). If by universal you mean a penis that fits just about all women and will be within satisfactory bounds to most of them, then my opinion is about 5.5 for white women, slightly less than 6.5 for black women, 5" or less for Asian women.
I anticipate someone(s) may say that porn women have bigger than typical vaginas. That could be, but unlike the penis which is seen, the vagina is hidden and therefore probably isn't as much of a factor in porn as one might think. I don't have any data to provide to help with that though. If you think that is the case then you can subtract whatever amount you think is appropriate from the chart in order to adjust it, but should think twice about adjusting it without data.