I have a Raspberry Pi 4 Model B with a Blokas PiSound Audio + MIDI Pi Hat.
https://blokas.io/pisound/
I ordered an x873 expansion board, and need its precise height including standoffs, so I can order a custom case that fits the expansion board, RPi 4B, and Blokas Hat together in a neat package.
https://blokas.io/pisound/docs/pisound-acrylic-case/#assembly-instructions