This isn't proper blocking, it's just pinned out while I look at it - and because it's a bit odd I'll identify it as the back of my Debbie Bliss shrug.
I did the armhole shaping at the end of the row this time - I don't like the raised bump effect you get from doing it the recommended two rows in. The left side, SSK decrease, looks fine. The right side is horrid. I think it's the combination knitting thing again. My stitches are seated with the legs at the back of the needle, so I knit through the backs of the loops to make the stitch turn the right way round, but it makes a messy edge decrease. I think I might need to slip them onto the left needle to turn them the right way around, then do a K2tog. I'll try that on the sleeves. I sewed another bit of knitting to it with mattress stitch and the lumpy edge didn't show, so I'm not undoing it.
Keeping track of every row is interesting. For one thing, if I didn't know I'd gone two rows wrong under the arm pits, I would have knitted two more rows at the shoulder to get to the expected length, then there's an extra row because I short rowed the shoulder, so that is a potential error of 1 CM on each side of the shoulder which is 2 CM overall - quite enough to spoil the fit of a garment. Will definitely concentrate on row control for a while! To this end, I knitted in a red thread at the armhole and another one at the start of the shoulder shaping, to help me see where I am.
In keeping with my new policy of trying to check at all stages, I measured the back and had a think about it. There is no schematic, but it is fairly close to the predicted measurements. My tension is fair - OK on stitches and slightly small (29.5 rather than 30 rows to 10 CM) on rows. Good enough to carry on. The back looks a bit small to me, but I know it is close to what it should be and I know that when I knitted one a size larger it was too big, so I'll make a front next and see how it all adds up.