I just made a short phone video to show the meters in operation:
In order to get a MIDI data stream to demonstrate the workability of 8 meters running simultaneously over one MIDI DIN cable (31250 baud), I programmed another MCU to generate it. That MCU generated sine waves, with a range of 0-127, then as each wave value would change, it output the value in a Control Change message.
My math on this is that all 8 displays could be updated about every 8 milliseconds. Given that a video frame rate of 30 frames-per-second (33 ms/frame) is generally adequate for smooth animation, 32 channels could be transmitted on one MIDI 1.0 cable. That would saturate the MIDI stream.