@mwaskom the other option here is to do:
```
if side in ['bottom', 'left']:
    ax_i.spines[side].set_position(('axes', 0 - spinesep))
else:
    ax_i.spines[side].set_position(('axes', 1 + spinesep))
```

A little more complicated, but would scale up and down with the figure size.