I had this same issue 3 weeks ago with the Eibach pro truck 2.0 coilovers. Only I didn't catch it at install because I had a shop do the install.

The problem you will have with the narrow bushing, if you don't use a washer, is that it will compress and bend the mount so that you will not be able to fit the correct width bushing on a different shock without out bending the mount back open (which isn't easy).

I had other issues with the coilovers and eventually gave up on them (although Eibach was responsive and helpful) and put in a 21 trd pro fox suspension (I only wanted 1 inch of lift) 2 weeks after the Eibach install. I did the install myself this time and that's when the narrow bushing bit me in the butt.

I had to use a large crescent wrench to bend the mount open enough to get some of the busing in, put a jack under the lower arrm and try to push the busing in until I could start to line up the holes. I then had to use an alignment bar to line everything up to get the lower bolt in. It was freaking time consuming and took longer to get the lower bolt to line up than doing the entire install would have if that bracket wasn't bent.

At this point, even if I wanted more lift I wouldn't put my Eibach coilovers back in. I'd go King, Icon, Fox adjustable, etc.