Only person to ever do it on USF was JewStyle.
Traxx did it on KSF along with a few other players.
No one, including JewStyle, was able to master it on USF.
The only time Jewstyle did it was actually when he first uploaded the vid (that got removed for some reason). He just got lucky and kept on doing it.
Everyone else who posted x2 kjump vids is using 3rd paty programs like speed hack, etc