I had the top case rack installed today at Motorzaak Amsterdam.
The rack is really solid! It comes with a relatively small top box but a bigger one should be no problem the frame is strong enough for that.
The main fixation are the bolts through the grab bar mounts but it's also connected to the rear subframe of the tail lights. The two tubes are welded together in the middle under the plate.
I asked for a matte black finish. Standard they use glossy.
Some photos can be found at my Empulse Flickr stream:
https://flic.kr/p/s96KSwAnd a link to the top case provided with the rack. It's the basic version.
www.coocase.com/showcase/s28_vivo.html