I'll have to respectfully disagree with you Tone, & please explain it to me real slow if you have info. I'm unaware of.
The bottom spring cup is tapered, with a stop where the end of the spring seats, to keep it from rotating. The top cup, is flat, with the stock rubber cushion.
It deosn't seem right to put the spacer on the bottom, when the bottom of the 912's is of the same coil shape, designed to engage the "stop" & the top is ground flat, to fit in the flat upper cup.
IMO, the spacers should go in the upper cup, replacing the stock cushion, which is designed to accept the flat end of the spring.
Just my opinion, waiting to hear what you're thoughts are...
And unless longer than stock shocks are installed, I haven't seen a set of 912's drop out. Not too sure that zip ties would be strong enough anyway.
Pic from Independent4X website: