Thank you all very much. As it turns out, 31C has become available (though 31A is occupied), so I've moved there. I've also set up an alert on EF for row 20. Really hoping that 20A/C open up.

Alternatively, if the middle blocks of rows 22-24 remain fairly empty, I'll try to move to one of the aisle seats there to have more personal space. Is there a way to check how many fare classes are still available for purchase on AA as there is on BA (so as to give a somewhat rough idea of expected load)?