The problem with short-row heels is that if you use the "default" recommendation of using 1/2 the total stitches for the heel, then the result is a heel that sits very low (doesn't come up over the back of the heel very far) and is quite tight across the instep. Depending on your foot shape, it may not fit well at all. If you google "high instep short row" you'll see this is a common problem!
So there are a few ways to address this. I've found four:
1. use garter stitch for the heel: instead of using stockinette, knit every row back and forth. Garter stitch is thicker and uses more wool over the same length of stockinette. Because of this, it is stretchier, and this may be just enough to improve the fit for you! As an added advantage, if you use the wrap 'n' turn technique for hiding holes in your short rows, there is no need to lift and knit the wraps. Just leave them where they are. They will be invisible in the final product. Here's a garter-stitch wrap 'n turn heel recipe. Of course, a garter stitch heel looks different from a stockinette one, so keep that in mind for your design.
2. use more stitches for the heel: instead of using 50% of the stitches for the heel, use 60%. When you divide the stitches into thirds when you turn the heel, adjust so that the middle third - the part that you never short-row - is still one third of half of the total stitches - unless you also want a wider heel.
example: total 60 stitches around the whole sock; "default" heel size would be 30 sts. That means middle third = 10 sts. For improved fit, use 36 sts for the heel (60% of 60), and divide the heel sts as follows: 13-10-13 (instead of 12-12-12).
This is hard to do if you knit 2-at-a-time on magic loop or 2-circs, because it involves either planning ahead when you cast on and putting more sts on one side of the magic loop than on the other, or moving stitches around when it comes time to knit the heel. It will also bite into the design on the instep of the sock. For these reasons, this isn't my favourite.
3. knit in a gusset: about 10 rows before you get to the point where you are going to start your heel, start increasing the number of sts on the side of the work that will become the heel. As a rough guide, increase the stitch count by 15% (rounded off to be an even number). Traditionally, you'd increase every other row on each side of the sock, but you can play with this (increases distributed evenly over sock? originating from central point?). note: depending on how many stitches you plan to increase, you may have to start increasing sooner, or maybe later. Or increase faster or slower than every other row.
Once you've finished the increases, you turn the heel over the new, larger number of stitches. Again, unless you want a wider heel, keep the middle "third" the same size as if you hadn't made those gussets.
When you've completed turning the heel, get rid of the gussets by decreasing back to the original stitch count.
note: Of course you can also put the increases on the instep side of the work, where they will not be participating in the heel construction. Again, remove them by decreases when you've finished turning the heel. Such a construction is a little more visible than hiding them in the heel.
4. knit a flap: you can knit a small flap (10 rows or so) before starting the heel. Just knit back and forth for a number of rows, using a chain selvedge, to create a flap. Then turn the usual short-row heel. When you've finished turning the heel you'll pick up the sts on the sides of the flap (about 4-5 of them on each side) and then decrease them away as you start knitting in the round again. This is basically a flap heel construction, but with a "mini flap". Knitters averse to the whole idea of a flap are unlikely to want to incorporate one into a short-row heel, since the whole idea is to get away from picking up those sts along the flaps. Right? So I'm not gonna waste more e-ink on this solution.
Final, important tip:If you want to try any of these ideas to see if they work, put a lifeline** into your knitting before you start the heel construction. Then if you don't like the end result, ripping it out is much easier.
**lifeline: thread a darning needle with some thin, slippery yarn - dental floss or cotton embroidery thread - and just run it through all the sts on your needles. This will act as a stopper when you rip out knitting. It will also enable you to quickly pick up the sts again.