Size 12 isn't a large shoe size? I thought it was.
Anyway, wasn't this topic JUST done?
In any event, whether there's a correlation or not, I personally think that there are enough exceptions to make it not worth noting. I have tiny hands, short fingers, tiny feet, tiny wrists, and I'm only 5'4" tall. My cock isn't massive by any means, but it's above average, yet all of the usual signs say I should be tiny.
Enough other people are exceptions to the rule to make it kind of pointless to use them, really. Until you see the fully erect cock yourself, you can't be absolutely sure how big or small a man is.