I have found that the stock KLX cable has enough adjustment in it to get a short throw action. I only work the lever with one or two fingers and the others are around the grip at all times. Just a little dab and it works great. At speed no clutch is necessary for up-shifts at all if you get a feel for it.
Maybe the condition of the cable and clutch disks has something to do with that?

RaceGass's trick is pretty clever though. If my cable were a little too stretched out, I might try that.