Please help. In the process of making granddaughter’s prom dress. The design is a halter top with a plunging V almost to waist. I have made three muslin drafts but no matter what adjustments I make, the V still gaps open. I have added fabric and taken fabric away. She is small busted, so it is not like she is busting out of it. For modesty purpose, we would like to keep the fabric close to the body. Any ideas or suggestions will be greatly appreciated.