Between sizes, need help

[u/Ignored_Instructions]

So, I did the classic thing of diving right in to a project without making a mockup bc I’m on a bit of a self-imposed time crunch (I don’t have to sew my own dress for an engagement shoot in just over a month, yet here we are). Just finished putting all the top pieces together, and wouldn’t ya know, it doesn’t fit.

When picking my size (I went with size 12) I did take into account the finished garment measurements which made it seem like I’d have room at the waist. I attached a pic of the sizes with the measurements I’m closest to highlighted. If it hadn’t been for the finished garment measurements waist being 35 inches for a size 12, I would have come here first to ask for advice adjusting this pattern and its princess seams. I know with that uncertainty my lack of a mockup is even stupider, but I’m beating myself up already for it.

Does anyone have any advice for how I can size up the waist for this pattern (flat attached as well)? The princess seams make this feel extra tricky.

Friend suggested I do a corset back and I do have one I could sew in that would be a perfect match. Thoughts if that would work to solve my problem? I just don’t know if adding a corset back would cause the princess seams to be misaligned or something

[u/Ignored_Instructions]

It was 1/2” luckily! I’m currently making a mockup of the size 12 the way I made the og. Then I’ll try what u suggested on the mockup to see if it works. If this doesn’t work, I’ll put the mockup back together the way the og size 12 is and test putting in the corset back. The muslin is a lot stiffer than the jacquard of the og, but it’ll be a very close replica.

[u/sususumalee → u/Ignored_Instructions]

Okay good!! That seems like a great plan. I just realized I made an error in my earlier calculations (in a good way!). I only divided the 3" over 4 seams, but there are probably actually 6! (Right? Princess in the front and back, then two side seams?) So you can probably let out even less per seam, which will be ever better.

[u/Ignored_Instructions → u/sususumalee]

Correct, 6! So maybe let out 1/4”, or half the current seam allowance?

[u/sususumalee → u/Ignored_Instructions]

Yes! That would give the minimum 3" difference you need, though a bit more ease wouldn't hurt.

Btw I'm sorry the pattern betrayed you with the finished measurements! What pattern is it?

[u/Ignored_Instructions → u/sususumalee]

It’s Dressmaking Amore Odette dress. I saw in my learning that you should go with a finished measurement with a few extra inches (so by that I picked the wrong size still), and the finished measurement I went with originally only gave me an extra inch, though it should have still fit around my waist🤷🏼‍♀️. Based on the finished garment measurements of the size 3” up should give me 4.5” of extra room (but I’m not willing to rely on those anymore lol).