Rear koni coilover install... something is not right

I have rear koni coilovers installed but the bottom washer keeps being turned inside out and basically shaves the rubber grommet into a thinner cylinder. I think there is something missing. It's setup up like this from the top down to the spring:

nut
washer
grommet
body frame
aluminum washer
grommet
washer
then the shock.

If you look at this picture, Rear Koni Coilovers you can see the top of the shaft is tapered and this is basically forming the washer to that shape. Which in turn starts cutting through the grommet. Am I missing something there so as to prevent this?

Thanks