[Self Drafted] Corset cover advice, please Sewing Machines Parts and Sales in Los Angeles

I’m working on a corset cover for a costume. I just finished the muslin and did a test run. The cover top and bottom seams don’t quite want to sit on the edges of the corset.

I’m going to add half an inch to the length, and hope that works.

The final material has a bit of stretch, and I’m hoping that will help, but is there anything else I could try?