Extending the back of jeans
From this
To this
The jeans on the left had been altered for my sway back. However the back rise was too short, so I kept trying to pull them higher at the back. So to work out how much I needed to add to the back I took my most comfortable jeans and measured the back rise - top of the band to crotch.
Favorite jeans back rise = 42.5 cm (16 3/4 in)
Uncomfortable jeans 40 cm (15 3/4 in)
Unpick yoke from jeans
Cut a new yoke adding increase at top.
Add section for side seam towards front so it tapers
Pin yoke to jeans with pins on jean side, so you sew into the original stitch line
Overlock yoke to jeans
Double machine stitch yoke to jeans
Right side of yoke attached
Close center back. Mine had a flat felled seam so I repeated on the new yoke. Close the sides, over lock and do a single top stitch.
Pin back back onto jeans
New yoke with additional length
You can make this same adjustment to any pattern you have. Comfort is a front and back rise that fits your body shape.
Happy altering
Judith Turner