If Ryu can backdash to eat the boom in midair, then so can Sakura since both of their backdashes are airborne during frame 10~18.
I tried backdashing with Sakura and she ate the Ultra.
It all depends on how you time the SB. I also hit Sakura with the ultra during backdash when I placed the SB as far away from Seth as possible.
I got both Guile and Sagat to backdash and eat the SB while airborne. Also of note, even though I figured it’s probably already known, is that the timing to set up the unblockable is different for different characters. i.e the same recording that worked as an unblockable for Guile and Chun Li did NOT work as an unblockable for Sagat… so I had to re-record.
I still couldn’t get Sakura to backdash out of Seth’s UB though.
I’ve done some testing and depending on which setup is used (and possibly even when the fireball is thrown), some escapes are not possible, or some might become possible. For example, I playedback a back-throw setup against honda and was unable to escape it using backdash. What happened is honda would backdash just out of range of the sonic boom, get hit by ultra and then sonic boom. Another thing that happened that was strange was I did the same setup against Sagat, spammed backdash on wake up (as sagat), and then held back once ultra flash occured, and Sagat stood and blocked the fireball (no backdash came out).
Also, midscreen legs -> hp sonic boom (confirm quick stand) -> ultra works on some characters. AFAIK it’s the fat ones though I’ve managed to land it on Ryu. Another quick stand setup that works is c.hp xx lp sonic boom, lp sonic boom (confirm quick stand) -> ultra (though why you would eludes me since c.hp combos into ultra). There may be other possibilities for quick stand setups.
Did some testing, the midscreen legs -> hp sonic boom (quick stand) setup works on the following characters:
Ryu, Ken, Rufus, El. Fuerte (crouch blocking), Dictator (crouch blocking), Abel (doesn’t work if started combo on crouching Abel?). This was only for a single CPU recording so it may work on other people. Here’s a link for Abel: [media=youtube]Brj6I_iZVsA[/media]
Edit: Also worked on Gen.