Unicorn HD HAT
Unicorn HAT on top of Raspberry Pi stack. (Yes, there is already an LED failure.)
Cable and Unicorn HAT mount so LED array can be on top next to track and Raspberry and servo HATs can be under the layout.
The 4 voltage dividers connect the 5v0dc interrupt outputs on the IO Pi HAT to 3v3dc GPIO pins on the Raspberry Pi.
Version #2 of the Unicorn mounting board rotates each unicorn 90º which allows the pixels on the edge to set closer. Looks better.
The purpose of the new display is to rotate each unicorn 90° so that the rows of LEDs fit closer together. The "track" drawn on the overlay is crude.