I just did this one on Seth, it seemed like the only way to get 3 stored fireballs in a combo.
f.j mp (height is very important, needs to hit somewhere on the thigh, I say on the bottom 3rd of the thigh.) release the upward fireball, mp, fb, mp, fb, mp, hk tatsu thing. 11 hits, 328 damage, 388 stun. I did it with c.mp in the video, I think standing/crouching is just dependent on where you are after the first fireball if the standing mp will reach, pretty sure it makes no difference to the dmg or stun.
Trickier version with 2 bars, I can’t complete it but seems possible.
Same jump forward mp on the thigh, release upward fireball, c.hp, release medium fireball, c.mk, hktatsu fadc, mp, release fireball into…whatever you want.
I play Ryu so… sorry about the tatsu whatevers I think you guys can translate!