If you can get systemsettings working, the setting would be in "Input Devices" -> "Mouse".
Otherwise, here's some example configs: ~/.config/org.kde.gwenviewrc <http://textuploader.com/ds0qs> ~/.config/kdeglobals (debian) <http://textuploader.com/ds0l7> ~/.config/kdeglobals (gentoo) <http://textuploader.com/ds0qa>
