Hi,
for me at least unrolling those 3x3 patches as you’ve proposed does not really make sense, as you would just replace the FC - classifier with a Transformer what seems kind of weird to me (as it’s not really a reasonable sequence - please correct me, if it should be so after all).
For your task, I would recommand checking out this paper 1. I am however not sure about how this approach could be adapted for more challenging OCR tasks.
Regards,
Unity05