It took a bit of hardware hacking, but I succeeded in putting a SSD, X825, RPi4B and a X728 into a X825-C6 case. It is now at the heart of my smarthome running on Domoticz more reliably than ever!
See the instructions on my blog https://robothuis.nl/2020/08/01/nooit-meer-last-van-een-stroomstoring-de-x728-ups/
The site is in Dutch but there is an English translate button!