Cups sewn into dress or plunging back bra?

Does anyone have any experience with cups sewn into their dress or with a plunging-back bra? My dress is too low-cut in the back for a regular strapless bra (see below), Page 3.

Essential Wedding Dress Underwear Solutions & Lingerie Hacks

BRA CUPS & PADDING: How To Make Your Competition Ballroom, Country

How to choose the right underwear for a backless bias cut wedding

Looking for opinions on what bra to wear with my wedding dress!!! Here's my dress and two options, the first are cups that stick to the material to add lift and the

Adhesive Clip Bra, Self Adhesive Backless Bra

The Perfect Bra Cup For Your Dance or Skate Dress - Sew Like A Pro™

How To Add A Built-In Bra To Clothing - A Beautiful Mess

What to Wear Under Your Wedding Dress - The New York Times

Bridal Corsets, Low Back Wedding Corsets & Bustier for wedding

Smooth Boost Plunge Bra

Brassiere with a Low-Cut Back Beige tulle bra with low back