Ubercorn daisychaining

Is there a detailed guide to daisychaining Ubercorns? I bought a pair and both work fine individually, but I can’t persuade them to work together.

The product page says “The pinout of the data in and out headers is (from top left, and from left to right) GND, GND, CS, SCLK, MOSI, NC (not connected), GND, GND.”, but the in and out headers are mounted in opposite senses (the grooves to receive the lugs on the cables both facing inwards), meaning the data cables can only be connected with a twist, apparently reversing the connections. If connected like this, the second Ubercorn remains blank.

Taking a set of separate F-F connectors and connecting 3-3, 4-4, 5-5 and running ubercorn-rainbow-2x1.py with DIP switch 1 set to on for the second Ubercorn, both light and the first looks as expected, but the second one has fairly random pixels and one column flickering.

What am I doing wrong?