Ok, so I just tested it: you don't need momentum, but it /does/ need to be against tall-ish characters (not May or Faust, for example.) The iAD timing is quite slow after 6H(1); just do the move and jump cancel it a few times to get an idea for when you need to start the iAD inupt. After the iAD, j.k should be inputted as soon as possible. It's worth mentioning that mid-screen this will only work from further away - if you're too close when 6H hits, your iAD will sail right over their head.