I think it’s #9 anyway.
The shoe change seems to have helped a bit but not as much as I hoped. The stages so far have been:
1. Ignore it (didn’t work)
2. Reduce mileage (didn’t work)
3. Stretch my calves (didn’t work)
4. Stop running altogether (didn’t work)
5. Dump the arch supportive shoes (worked a bit)
I am hopeful this requires only a six step plan rather than a seven step plan.
I still think that attacking it from the perspective of underpronation is correct. It is noticeable when I walk around that I am subconsciously hesitant to flatten my right foot fully and instead end up balancing on the outside edge of it. I think that the fact I seem to have had a lot of minor secondary issues in my right foot as well as the metatarsalgia suggests a broad biomechanical problem, which underpronation would fit. And I have reasonably high arches anyway.
My current thinking is that I should be trying to work out how to signal to my body and mind that it is ok to let my foot flatten out a bit. Trying to do it consciously is really weird.
So the plan for the next few weeks is to hit it with lots of balancing exercises – i.e. single leg squats, single leg romanian deadlifts – and hopefully as my body gets used to flattening my foot during those it will start feeling more willing to flatten it when walking/running.