Choosing where you want the Kunai to land is all down to feeling and practice.
You have two choices after an untechable knockdown:
- When You Jump
- When You Throw The Kunai
The later you throw your Kunai, to closer it gets to landing as a cross-up; the later you jump, this is also the case.
You should be able to delay your jump and Kunai until very late, to the point when it looks like you don’t have any time to ~ the problem with delaying your Kunai is that the more you do, the more unsafe on block you’ll be.
Perhaps I’ll upload a video of the different options, but in a match I can choose where it lands 'cause I’ve been using it so much. There are 5 different timing I use, and I just shuffle between them.
- Throw Kunai at Jump peak (no cross-up)
- Throw Kunai at delayed Jump peak (no cross-up)*
- Throw delayed Kunai with Jump (cross-up)*
- Throw delayed Kunai with SJ (cross-up)**
- Throw Kunai after jumping right before wake up (punish crouch-tech/non-reversal wake-up)
- = depends on opponent, timing is different 'cause characters get up at different times (Cody gets up slowly, Adon gets up fast)
** = Super Jumping changes jumping angle.
Anyway, this is all theory. You gotta keep practicing until you get a feel for it. Bare in mind doing so online will give you the wrong timing due to lag. Vortexing works extremely well online, but don’t expect it to be as effective without the lag.
EDIT: ah yeah, you gotta remember that the Kunai has to already be there when the opponent wakes up, otherwise any old reversal would get them out of it (including a bastard auto-corrected Ultra). The Kunai should hit like a meaty would ~ in most cases anyway.