I like Topol's idea of a low heel for the ankle-high boots, though the outfit looks everyday sporty (think work).  Then again, with the right fabric, the outfit could look a little dressy (out to dinner), so a very flat heel might not look right then.

As far as a high boot goes, I don't like the look of it right up to the knee.  I think the middle of the widest part of the calf would be high enough . . . say about 2 inches below the knee.  That way they wouldn't interact directly with the outfit.

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OK . . . Where's my chocolate?

Butterfly Dezignz