Backless dress undergarments?

My daughter is a 36DD. The bodice of her dress was fairly similar to yours. Although, her dress had a ton of built in structure (I can't tell if yours does). Her alterations were done at the bridal salon. They took her dress in a little at the side seams to get it as tight on her ribcage as possible, then they ended up using two sets of cups/pads. They sewed a larger set of push-up cups (the last thing my daughter ever thought she'd need as a DD! ) into the dress so they were just below daughter's chest -- they helped lift her up. There was still a little extra room toward the top of the bodice, so they sewed a set of smaller cups near the upper-outside edge of the bodice. As a result, her natural chest fit fairly snuggly into newly padded bodice of her dress. She looked awesome. (She tried every stick on and backless bra option she could find and nothing worked for her.) Good luck!

I've been having the same issue. I tried sticky bras but none of them did what I wanted them to do, pull in from under my arms and up. I was thinking of something like the bridal bra, but then I thought about how easily (or not easily) going to the bathroom would be. I decided to purchase the Skims sticky tape. I read reviews on more generic bra tape and they all said they gave great support, but taking if off was extremely painful. The reviews on Skims were great and people were saying it came off painlessly. I haven't tried the product yet, but at least I know with tape I can use as many strips as I need and customize my own support options.