I enjoyed watching this video so I looked out your video on the Model D attachment as well as I haven’t seen that working either.
Apart from low sales, what must make the Lightening Repeater particularly singular is that it detaches from the machine and would get lost. The Model D remains fixed.
The advantage of not having to have a dealer install this repeater, became a disadvantage when the machine was first put away in the attic! The repeater would have been immediately separated from the machine.
It appears that the Lightning repeater would function on Edison phonographs equipped to play 4 min. cylinders as well as the 2 min. cylinders. The changes to the top pulley and feed shaft of the 2&4 min. Home and Triumph phonographs seemed to have made most if not all the non-Edison record repeaters impossible to work. If someone had an aftermarket repeater on a 2 min. phonograph and wanted to convert to a 2&4 machine, they would have to remove the repeater. That may also help to explain why so few show up.
Dan Z.