Krazie posted about the reverse hitbox a few months ago. You can get a knockdown that will let you hit the reverse 2 after 121, 121~AA throw(which I believe was what krazie was doing) 121~teleport, and 123.
You can also convert a reverse 2 hitting midscreen very easily with a follow up 12, which I have seen GGA Han doing several times in the last few videos he posted.