Thanks... I think I have some old truck liner rubber that should do the trick. Crazy the Koni didn't provide a better way to secure the shaft.
I usually use a thick piece of rubber and a pair of vise-grips to hold the shaft on the rear dampers.
I read a post you made on the rear Koni inserts not having any feature to keep the shaft from spinning while tightening 17mm the shaft nut. I was trying to install mine today on my '02 WRX wagon when I noticed that, and thought Koni must have skipped a step in manufacturing. I have an email in to Koni, but do they really not have anything (like the front inserts have) and leave you to somehow clamp the shaft itself to tighten the nut?