A 2.5"-3" heel is perfect for me -- actually, more comfortable than flats (I think I have a higher arch, too). I don't go above 3.5", though, and I don't even like to wear those, since I am standing most of the day.
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"We live in an age where unnecessary things are our only necessities." --Oscar Wilde
I like 4" if I don't have to be on my feet for extended periods of time. If I'm on my feet, I try to do a 4" with a slight platform, so it doesn't feel as high. Otherwise, without a platform or wedge and being on my feet, I like 2 1/2."
I can do a 4 inch stiletto for special ocassions and usually wear a 2 or 3 inch. Oddly enough I can run in heels better than in flats, probably because I wear them so much of the time.
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"Life is much too serious to take seriously"- Nikki Giovanni
Jeez I wish I could wear heels! The highest i can pull off is like an inch! I am 5'9 1/2 to start with. I don't wanna be any taller, but the shoes are so cute!!!