I am thinking the real fix for GT5 shadows should be of hardware nature, not software. Try and turn on nice shadows on a high-end geforce 7 series PC videocard and you'll get a huge drop in performance, it also depends on the CPU processing capabilities. PS3 is already old and not up to PC graphics today, unfortunately.
high end Geforce 7 series ???? lol
re shadows just let us turn them off (as an option) - surely that would be very easy to implement