Things started off great, then not great... but now they're great again.
When I first flashed the Power Controller it worked just fine. Then suddenly it started giving me error messages and HiFiBerry wouldn't load. I read as many post as I could to figure out what was going on, but ended up going to bed frustrated. Then I woke up, powered it up to start trouble shooting and it worked just fine. So odd, but I won't complain because it's working great.
I built up a simple mount and incorporated the Power Controller with some tinted Perspex I bent with a form and a hot air blower.
Currently it's mounted on a Pi3 instead of the Pi4 because I'm using the 4 for a different project and the 3 was being used as a Pi Jukebox previously so it just made sense to use it this way.
Next steps are to trim up the mounting hardware, obtain some proper binding posts, and match some better speakers to the system.
It was so much cheaper to build this up than to replace the valves in the power section of my tube amp... and it sounds great.