It is quite hard to see from the photos but the front of this purchased knit sweater was longer than the back, (which might've been why it was in the sale). This might be good for someone with a larger bust but on me it was not.
This photo is from the back, showing the front being longer.
I wanted to keep what length I could at centre back so unpicked the original coverstitching, pressed it flat, drew a new curve with my French curve, cut it off and then rehemmed it with my coverstitch machine.
The front and back are now the same length and curve very slightly to the sides.
* note on unpicking coverstitching.
It is in essence a twin needle chain stitch so if you can get it started the underneath thread will unravel for long sections, this goes for both RTW and home coverstitched items. I find where they have overlapped the stitching and unpick about an inch with my seam ripper. Then I get the underneath thread and try pulling it, eventually one side will start to come undone and I pull it as far as it will go. On this top I unpicked the overlap, the opposite side seam and one other place where it had caught, and just pulled all the rest.