Paul,
Thanks for the drawing you sent. Previously the way it was explained, it sounded like the springs were the only thing providing the force on the axle gears. This just would not work.
I see now they use the same principle as a normal clutch pack LSD. The cross pins run up the ramps in the block as torque is applied. This forces the block against the side gears.
I can see they would work with lower power applications.
I APOLOGISE PROFOUNDLY FOR DOUBTING YOU 1200 RALLY CAR!!!