You have seen this FS1R controller on my youtube
and you probably read the interview on amazona.de: https://www.amazona.de/mega-hardware-controller-fuer-yamaha-fs1r/.
There was much resonance to this and I decided to build 2 small batches for a couple of FM-enthusiasts. These two batches of controllers are delivered now, I do not plan to make further devices.
Thank you for your interest!