When I say "taking in the inseams", it sounds like a simple thing to do - but it's not if the inseams are flat fell seams. Because they are, it meant unpicking the topstitching and seaming of the inseams, then unpicking the outer leg seams in order to restitch the inseams and re-do the flat fell stitching. In other words I practically took them apart and put them together again.
Unfortunately I don't have a non-blurry photo of the improved back view, so you are left with the saggy old lady butt view in the last post.
I made a second pair of jeans, this time using some rigid (but not raw) denim. It was way easier to work with than the super-stretch denim because the rigid stuff doesn't stretch out when you stitch over it.
Unfortunately I have not learned from all of the pants-making that I must do a fisheye dart on the back leg pattern piece in order to remove all of the excess fabric that results (which comes from having an apple-shaped body) -
Because it's rigid denim, simply taking it in at the inseams will make them uncomfortable to wear, so I'm thinking of just sewing a massive dart in the back of each leg so that they look a bit like this -
See - they are much less wrinkly now. But there is a crease under each bum cheek (which will become a seam if I proceed with my possible plan).
In the meantime I have been wearing them in and they are pretty comfortable now, though not as comfy as the leggings-like fabric of the stretchy jeans.