I am a total know-nothing when it comes to sewing, so here is a question for those of you with some expertise.

I got an Esprit sheath dress that I absolutely love. The problem is, it is so form-fitting that it feels like I could literally split a seam if I sneeze. Before I return it (they don't have any more of them, so a larger size is not an option), here is my question. It has a long zipper down the back, and I'm wondering if my tailor can just get rid of the zipper and insert black elastic instead. Or keep the zipper and also insert elastic along the sides.

The dress is silk and has a lining. Would it work to do what I'm suggesting, or should I just give up, dry my tears, and return it? TIA for your thoughts!