All of the physical features, other than the cock itself, can NOT be used to measure how big a guy's cock is.

I'm 5'4", with tiny feet, tiny hands, tiny wrists, and short fingers. Despite this, I have an above average dick (or, according to what people online have told me, a rather big cock; I've measured only 7 inches, even though people on this site have accused me of being longer).

I do have a rather low voice, and a really big head (the one above the shoulders), but I seriously doubt those are good ways to tell a man's size.

Seriously, if I'm anything to go by, you can't rely on body characteristics to judge a man's size.