hemming necklines (or just curves)

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so i'm trying to hem up the neckline of a tank top that i am currently working on right now, but i am predicting that the cloth might end up a bit wonky, such as maybe wavy or something like that.. since it is not a straight edge that i am hemming, like a bottom of a shirt.. and its actually a curve like a U since it is a neckline. can anyone help? tips on hemming necklines? thanks in advance! <3

xposted to t_shirt_surgery & sew_hip