I am the opposite of you – tall and curvy. I think my height is a plus for the tunic, however, the curves on my upper half made nice fitting a challenge. I think this yoked style of top is actually better on those with smaller busts, but as I love the style, I persevered and made two (photos in a sec).
I think you’ll find that you won’t need to lengthen the bodice if you’re smaller-chested. It will be easy to lop off some of the hem if you decide you want to go shorter. I did mess with the skirt on both of my versions. If you use a nicely draping fabric, the gathers aren’t too much. But I made my first out of a substantial linen and it did not play nicely with the gathers, so I did an inverted box pleat instead. It is a little tough to reduce the width of the skirt after you’ve already cut and sewn the pieces, if you want to maintain the hi-low hem. But since you are short, you may decide you want to even out the back hem anyway and then you could just try as you go.
#1: http://www.flickr.com/photos/23557464@N03/10396700766/ (sturdy linen, in which I did not lengthen the bodice)
and
#2: http://www.flickr.com/photos/23557464@N03/11941862786/ (floaty double gauze, in which I lengthened the bodice and took the skirt in a little).