Adding boning to an evening dress

[sewmolo]

Hello! I have a silk dress with princess seams, sweetheart neckline and v-back. It's interlined in brushed cotton, but I'd like to add boning to it to give it some more structure. Please can someone help me with working out which seams to add boning to? I already have spiral steel boning left from another project and am planning to attach casing to the seam allowance.

In total the dress is made from 8 panels (4 front, 4 back), and the zip is in the back. Do I just bone the waist portion of the dress, or should the boning extend up into the bust (along the princess seams?) And what do I do with the zip - boning on both sides, just one side, or neither?

Also is it worth adding a grosgrain internal waist belt for support?

Thanks a lot for your help, any other suggestions are welcome!

[Ohsewsimple]

Hi @sewmolo.  Questions questions   
What sort of silk is it?
Does it have a lining as well as the interlining? 
Is it a strapless design or does it have sleeves or at least come up to the shoulders?   
What is happening to make you want to add some support?
All these will give us some idea of what you may be able to do with it.

[sewmolo]

It's charmeuse interlined with brushed cotton, no lining. It has straps that are cut from the same panels as the bodice (but I need to redo them, and am half tempted to take them off and make it strapless).

The main issue is that it's a 50s style but doesn't have that nipped in waist look that I'd like it to have, and the fabric around the waist is creasing (which I know means I need to let out the seams, and I will, but that will make it even less nipped in).

[Ohsewsimple]

You can only really have a waist stay if the dress is designed to be fitted at the waist. 
If the dress has straps then it might not be close fit enough to adapt it to a strapless design.  There would generally be different amounts of ease for these. 
There are many different ways to add boning.  If you have seams in the brushed cotton you could add your casing to that.  I wouldn’t add it to the silk.  It’s quite delicate and you’d probably get some show through.  Boning over the bust is an option.  It all depends what works for you and the dress. 
I’d bone either side of the zip.  One side would look odd.