I tried everything to stop the blades going over the edges, even changed the wheel in the wiper motor - no success. The drawing for a "parallel mechanism" (pantograph) must still be somewhere...
Against the judder - and the scratching of the glass by the metal on the wiper blade !! - I stretched the springs of the arms until the blades touched the glass only lightly; also not good because they nearly lift off at high speed.
Frank