Poof! Hips came flaring out. Obviously I need hip gussets. Sitting down became instantly easier. Corset sat down further than it did previously, so I need to lengthen the corset a tad. Ribcage is still too tight, but I think that can be solved with a larger corset.
Now I have a decision. I could use this same corset pattern (which is actually based on a later version, 1870s, actually), or since I have substantial hip flare that I didn't want to admit I had, I could try the 1864 corset from V&A that I've been dying to try out:
I don't have blue silk to make it out of (and I want a white corset anyway, since I plan on some white sheer bodices in the future) but it is such a pretty style, don't you think? I'm not sure how it would feel with the bones ending so sharply at the hip like that. I fear it would dig into my waist. But it's still a beautiful corset.