Same here dude - I'm about 5'8" too, and a girl can only be marginally taller and I lose interest. If I have to look up even slightly when talking to her, then my attraction for her wanes.

Although if I saw that she was wearing ridiculously high heels, making her that inch or two taller than me, I would bust her on it and if I got to see her again, I would insist she wear flats.

Much love,

Craigus