People are not shaped like hangers. Luckily for us, huh? This is why some shirts or dresses will look horrible when strung on a hanger, but look great when worn. You need the curves that come with a human body to fill out a garment and make it look good. This is why hemming a dress while it’s hanging on a hanger just will not work. Or why lining up buttons to go up the back of a dress will get you uneven tension through the body once the dress is put on.
This also explains why it doesn’t always work to turn a fitted garment inside out, put it on, then pin your adjustments. SOME people are pretty balanced left to right, but many people are not. I have a scoliosis curvature in my back that is not really noticeable. However, it does cause one shoulder to drop slightly lower than the other. Thus, if I were to fit a bodice to myself by turning it inside out (which puts the left side of the bodice onto the right side of your body), I would end up with one really tight shoulder and one really loose shoulder once the adjustments were made.
How to fix this? I usually do one of two things. Option 1: Put the garment on (right side out), pin where you want to make changes. Remove the garment and carefully transfer the folds and pins (re-pin) so that the seams are going in the correct direction. Option 2: Sew the garment with flat felled seams on the *outside* of the garment. (I’ve been told there are examples of this in period, but I have not done the research myself.) With flat felled seams on the outside, you start by stitching the garment together *wrong side to wrong side*, then you make your adjustments as needed (which is easy now because the seams are accessible on the right side of the garment. Once you’ve got everything fitting right, you trim your seam allowances and fold them to create a flat felled seam, then stitch away. The end result is a very nicely fitted garment.
Now, these are simple fixes for somebody who is only *slightly* asymmetrical (as we all are, really!). What if the differences are more pronounced? The kirtle that I will be soon be sewing will have to be fitted to a lady who has hips that are not level, a leg length discrepancy, and one arm about an inch shorter than the other. How do you accommodate these kinds of differences? The same way as you do the slight differences we all have. Only now it is even more important that I don’t “sew for a hanger”. Every step of the way, the kirtle will need to be fitted to her to make sure that it is fitting her body and not some unrealistic hanger. We will have to check fit at her shoulders, the side seams, the waistline, and the hem. We may even have to adjust how the skirt attaches to the waist so that, when it’s on, it looks level. When I make the chemise, one sleeve will be noticeably shorter than the other. When the dress is hanging up, it will probably look uneven. The skirt hem may look crooked. But this is NOT the time to “fix” it. When she’s wearing the dress, it will be balanced and even.
One other note: if you are sewing for somebody who wears braces, shoe lifts, orthotics, or anything else which *could* change the shape or posture of their body when they are wearing the garment, make sure they are wearing those same things when you are doing the fittings. An orthotic in a shoe may not seem to make a difference, but I’ve seen it change a dress from “floor length” to “tripping over it”.