You can see the difference in size between the steel type kett and the Kross. The black Kett seems dwarfed by the bigger and much heavier Kross.
New in 2016 although not updated in the catalog is a new tandem part designed for the single hole mount.
There is a design flaw with this however. If you remove the kett at the back and leave the tandem piece on it will very quickly strip the teeth on your rear cassette. I had to argue a lot with the dealer to get this replaced. Eventually I wrote to Hase and they asked the dealer to replace it.
Sadly since fitting the new cassette it has worked loose after a few hundred kilometers. This will involve a lengthy trip to a dealer as the rear suspension and drive have to be separated, the differential removed and then the cassette tightened. Not a two minute job.
Here is the first item that has been adapted for the trike. I have used the single strap supplied by Hase for folding the trike and put it through the hole in the tandem coupling. This stops it rubbing against the rear cassette.