Gau dressed in Locke's outfit

I'm still not 100% sure or confident that this is what you mean, but if you want to speed up the time it takes for the Jump skill to activate, which is how long the character stays in the air, then this is what you'll want to change.

From the C2 disassembly:

(Data - Time to wait after entering a command until character actually
 performs it (iow, how long they spend in their ready stance).  This
 value * 256 is compared to their $3AB4 counter.  I'm really not sure
 how this applies to enemies.)

C2/067B: 10   (Fight)
C2/067C: 10   (Item)
C2/067D: 20   (Magic)
C2/067E: 00   (Morph)
C2/067F: 00   (Revert)
C2/0680: 10   (Steal)
C2/0681: 10   (Capture)
C2/0682: 10   (SwdTech)
C2/0683: 10   (Throw)
C2/0684: 10   (Tools)
C2/0685: 10   (Blitz)
C2/0686: 10   (Runic)
C2/0687: 20   (Lore)
C2/0688: 10   (Sketch)
C2/0689: 10   (Control)
C2/068A: 10   (Slot)
C2/068B: 10   (Rage)
C2/068C: 10   (Leap)
C2/068D: 10   (Mimic)
C2/068E: 10   (Dance)
C2/068F: 10   (Row)
C2/0690: 10   (Def.)
C2/0691: E0   (Jump)
C2/0692: 20   (X-Magic)
C2/0693: 10   (GP Rain)
C2/0694: 10   (Summon)
C2/0695: 20   (Health)
C2/0696: 20   (Shock)
C2/0697: 10   (Possess)
C2/0698: 10   (MagiTek)
C2/0699: 00
C2/069A: 00           

E0 is a high value, which is why the character stays up in the air for so long. You would just put a lower value to your liking. So go to C2/0691 (offset 20691) in your hex editor and change the E0 to something lower.

If this isn't what you're trying to accomplish and you mean to shorten the actual animation timings, then that would be done by shortening the 'loop starts' back in the Jump battle animation data - you'll see loop start, and then lesson the amount of loops it does, basically...