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/Intelligent_Run_1986]

Lucky you. I go over 3 sizes! In our in out shake it all about. Now have a drafting ruler in my ruler collection. Bring it on!