I've timed it for when her elbow reaches the corner and her feet start to drop, respectively to each slide.

I'm sure someone's found this already, but I haven't watched any runs yet.

If you hold left or right then melee (running melee or in the air) then jump while a spark is lit, you can skip the 1 second animation to aim. You can still launch in all 8 directions. This should make the Boss Golzuna (cross bomb) alot faster, as the chance to shinespark it is pretty difficult.