Why don't use a keyboard shortcut with this script ?

script:if ( moi.ui.mainWindow.viewpanel.mode != 'split' ) { moi.ui.mainWindow.viewpanel.mode = 'split' } else { var viewport = moi.ui.getViewportUnderMouse(); if ( viewport ) viewport.viewpanel.mode = viewport.name; }

Nothing can beat shorcut speed for navigation stuff ;)