Ah THAT thing ;-)
One thing that immediately put me off was the fact that the 2mm banana connectors do not fully insert into the jacks.
I can't help but figure how I snap those with my elbow. That's only me of course.

Here is a long talk from Hainbach with Prof. Bernd Ulmann, one of the project's initiators, and Hans Kulk of Willem Twee Studios. FF to 10:30 for appearance of the guests.