OK so I finally got around to installing my brandy new Hepco & Becker top rack. It was actually really easy.
First, remove the seat.
Second, undo the two nuts that hold the little plastic U-lock tray in place over the rear fender, remove the tray and set it aside:
Third, loosen up the upper shock mounting nuts. You don't have to remove them but spin them back a bit so you have some room to work. They are 17mm.
Now, loosely mount the rack to the upper shock mounts. From the outside in it should go like: nut -> original washer -> rack -> shock -> grab handle -> frame. Like this:
Let it rest on the taillight while you get the other bits together.
Grab the support plates from the kit:
They are left and right and it matters. Basically these guys are why you removed the U-lock tray. Insert them behind the frame tangs, between the frame and the rear fender. The threaded bit should face toward the fender and the flat bit toward the frame. The rounded bit will tell you which is left and which is right when you try to mount them.
(BTW, if you have the original US-market reflectors, you need to remove them before this part.)
The support plates go in here:
This is looking from the top down with the U-lock tray removed. You will have to put them in from the top while supporting them from the bottom so they don't fall out.
Next you grab a bolt from the hardware kit, slap a washer on it, put it through the rack, put the spacer between the rack and frame, then thread the bolt into the support plate through the hole in the frame. Like this:
It's a bit tricky getting everything lined up but it works. You may want to run the bolts through the support plates before installation to make sure the threads are clean.
Once you've got both sides together, snug everything down but don't let the bolts hit and scratch your nice chrome fender:
The upper shock mount nuts should be torqued to 43 ft-lbs.
Now you've got a rack:
And you can mount your H&B top case to it:
The mounting/locking mechanism:
Super easy to install, looks great and feels very robustly made. Hope it lasts a long time.