Player velocity reduction on attack | SpigotMC | Page 1

Hello,
I'm trying to make a plugin to remove unfair advantage of high CPS in PvP. Specifically, knockback reduction mechanic, which multiplies player's velocity by 0.6 every time they click another player.
I want to replace that 0.6 with my own formula, but its located in NMS class.
Only idea I have is to listen for attack packets, and divide player's current velocity by 0.6 to nullify this effect, than apply my formula, but I think it will be very buggy and inconsistent.
Is there any other way to do it without patching server jar? Thank you for any help.

#Player velocity reduction on attack