craftgrrl | vinyl bag

I'm going to try sewing a double-layer vinyl bag tonight with a cut-out on the first layer so the under layer shows through.

My question is, (to any of you who have done this): do you hem the sides of the part you cut out or just leave it rough? It seems like it would be hard to hem the sides of a star or butterfly....right? And since vinyl doesn't fray, it seems to me that I should just leave the edges raw.

sorry no pictures - they'll come later (if what I do turns out awesome. haha)

Thank you!