Join Date: Oct 2006
Location: Stuttgart, Germany; Portland, Oregon
I never really understood the purpose of that stepped washer.
I had the problem that with that step facing the undertray, the bolt would not clamp the undertray tightly, causing it to rattle.
So I started installing those washers with the step facing the bolt head and I never had an issue (that was about 10 years ago).
I might as well just use flat washers if I ever need to replace the original ones.
Just make sure you hand start all the bolts first to get everything aligned before tightening them down
If I die, my biggest fear is that my wife sells all my toys for the price I told her I bought them for...