I had this exact issue. I originally bought the bars a year ago for my 2008 V6 Vert. I put them on and the bushing was too narrow and started bending the bracket. So I put just one washer on the outside. Once tightened up I kept getting a loud "thunk" from the links.
I too called Eibach and got the "it's ok" response.
What I did was to measure the difference just like you and go get a couple of washers to make up the difference. It worked fine and I sold the car and kept the bars. I bought a 2013 v6 Vert and put the bars on it with the same issue. Once again I used washers to space it and it has worked perfectly for 10K miles.

 

Did you use metal or rubber washers? Seems like rubber would give a tighter fit. Yeah, I still need to do this to my car but since I can't get under it at my house I have to arrange with a friend to let me use his driveway.

 

I just used Stainless Washers. Make sure you torque everything to the right specs or it will make noise.