Don't worry about your frame type or size. Most anime characters are thin, even tiny. And you could still appearance adorable cosplaying as them, even in case you're not! Be assured on your dress.
Be prepared to address grievance, perhaps even via thinking of comebacks in advance. But the element is, most humans will love and praise your costume at a conference! So, do not worry—what's the opinion of 1 bully weighed towards the ten folks who say "high-quality costume"?