I'd go for the athletic figure. I think that suits Rainbow Dash a lot better then an hour-glass shape with big boobs and broad hips.
For an athletic figure the bust and hip's should be about the same width. Say, if the bust is about 80 cm, the hips should be about 80 cm too. And the waist maybe 65 cm. That would give you a column body shape, which I think is the most common body shape for athletic women. I have a very athletic figure, and my measurements are 84-63-86, and I'm 172 cm tall. I hope this helps somewhat.. ^^
Cosplay's I'm working on:
Shion Sonozaki (school uniform) - 100% done - for Banzaicon 2013 skit
Shion Sonozaki (Angel Mort uniform) - 100% done - for Banzaicon 2013
Himiko (Manga chapter 45 front pageversion) - 100 % done for Banzaicon 2013
Asuna Yuuki (Undine version) - 100% done - for Banzaicon 2013
Ikaros (Uranus Queen version) - 50% done - for Free Comic Book Day 2013
Morgiana - 10 % done - for Desucon 2013
Princess of the Crystal - 20% done - for ??
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