How to Make an Off-the-Shoulder Bodice Functional? [Pas Sewing Machines Parts and Sales in Los Angeles

I’ve been working on a muslin using Past Patterns #704 1863 Ball Gown Bodice. It’s meant to be fitted just off the shoulder, so that’s what I’ve done. I thought I was starting to get everything fitting fairly well (excuse the wonky seams – I’ve had to take it in quite a bit). Then I tried raising my arms and found that they’re pretty well pinned down by the shoulders. If I add in a little more ease at the shoulder, I can raise them more, but the bodice pulls up. If I add in a little more, I can raise my arms, but I lose the nice fitting across the bust and back.

I’ve taken some pictures of how the muslin fits with the intermediate amount of ease at the shoulders. Does anyone have any suggestions as to how to make this fit better?

http://imgur.com/a/1wLc2

Thanks!