This is an extremely barebones, first-pass POC that shows how an Arduino Leonardo could be used to emulate a RailDriver's main analog inputs for Run8.
To use this project, you'll need HID-Project by NicoHood. This can be installed from the Arduino Library Manager. You also must modify your boards.txt file to reference the Raildriver's VID and PID:
...
leonardo.build.vid=0x05f3
leonardo.build.pid=0x0d2
leonardo.build.usb_product="Emulated RailDriver"
...The RailDriver's HID documentation can be found here.