My K12S came with a beautiful Hepco & Becker tail rack installed. After a little research into the brand, I found that they have some topcases designed to mount to the rack. I found precious little info or pics on the web specific to the K1200S, so I thought I'd post this.

The rack itself it is extremely sturdy, and mounts to the subframe, replacing the OEM grab handles. It's shaped so that IMHO it looks really good on the bike, not out of place at all. I can't comment on ease of installation, since the previous owner did it.

I bought the Journey TC40 top case, also known as the 40L or 40LT. It comes with no additional hardware, the mounts are built-in to the case. It slides onto the rack, and closing a stout latch secures it to the rack. The case appears to be of high quality, the only fault I can find is that the lid latch is made of plastic. I'd think that a metal part would be better here. The case does appear to be well waterproofed, with a nice rubber seal all around.

Appearance-wise, the case looks as good on the K1200S as any topcase possibly could. (The Squid's Law clearly states that C=S-P, or Coolness = Sportiness - Practicality.) I don't think this case subtracts too much 'S', while it does add significant 'P'. Mounted on the HB rack, it's in close and tight to the tail, not hanging out in the breeze like some do after rack + adapter + case is fitted. There's a large reflector on the back (not a light). The top panel is a silver that happens to pretty closely match the light silver of the frame and stuff on my gray KS. In other words, while it doesn't match the tupperware, it doesn't look out of place. The outward size is just right; it looks pretty stock. The OEM panniers still mount just fine with plenty of room.

My gym bag and soft briefcase + macbook fit well inside. This is the main reason I got this, for commuting. With the other stuff out, my helmet (Large Shoei RF-1000) takes up about 3/4 of the case.

Here are some photos with the box mounted:

And the rack alone: