Headlong

I got the YME-H0789-00-20 set from my dealer and tried to mount them on the front. As you can see in the pic, the threading is 2.5 cm long (sorry, I'm European, it's almost an inch, I think). That is too long to fit between the side panel front and back sides, even with the fat spacer on the outside. (What were they thinking with those annoying lock washers to hold the backside?!!!!) Am I doing something wrong? I see many places that apparently the same set is referred to with part number YME-H0789-00-10. Could it be that model has shorter threading? I see a solution is to put an extra spacer on the outside, but I didn't have any that would fit.