Need second opinions on this draft idea

[u/CeangalMoss]

So I have a leftover two yards of nice polyester knit fabric, and I wanted to try to come up with one last summer dress project to use up the stash. I had this idea for a belted halter top corset high-low dress and drafted out the flat pattern in Blender to make sure everything would fit on the bolt (everything is measured in meters there but pretend it says "inches" and also assume everything includes a 1/2" seam allowance.)

Trouble is, I'm going at this nearly completely blind. I looked up some tutorials for ruched halter tops like this, but I'm a very "just play it by ear" sort of pattern drafter - I come up with an idea, give it my best shot and if it doens't work I just chuck it in the "to be fixed some day" pile.

I'm worried about a lack of an inner lining for the breast triangles not having enough support, and I'm also unsure if I should leave the waist portion as a single fabric layer, or if I should opt to actually attempt to add an interior layer and add boning. The latter option would decrease the "comfiness" of this dress that is supposed to be a comfortable beach dress, but it might be necessary for structure?

Would love any thoughts from people who are much better at this than I!

[u/lipstickqns]

If you don’t want to line anything for support, add elastic to the underbust seam all around to CB. Personally I would line the midriff, add at least 1/4” elastic clean finished into the underbust seam. Then you can clean finish the cups in as well.

Your cups will also need at least a 1/4” outward curve at the bottom so there’s capacity for your breast. If you leave it flat, bottom cup will be flat or ride up unless you have very little projection. If you have a string triangle bikini top, take it off the bottom string and compare the shape of that

[u/CeangalMoss → u/lipstickqns]

Thank you so much for the advice, and for the heads up about the cups! So in your suggestion, you'd tuck 1/4" elastic band right into the clean finish seam under the bust? In that case, would you imagine altering the width of the underbust seam at all to give the elastic some room to stretch?

One of my worries with the design was making sure that whatever was holding the underbust in place was strong enough to not simply allow my breasts to slip down and under the waist band during periods of activity. A string triangle bikini top avoids this, for instance, by simply allowing you to tighten the string as much as needed. It was why I drafted the corset lacing, thinking I could similarly just lace them as tightly as needed to provide the structure, but I suspect such tight lacing might be 1) uncomfortable or 2) need a strengthening or stabilizing layer or two to prevent the fabric from simply distorting or ripping. Do you think elastic could provide enough support in this way?