So September 5th is here and the Windows 2004 (May!) update finally become officially available for my Hi10 Plus. Despite my concerns I managed to install it without any issues. Hurrah!!
I first backup up my entire system using Acronis True Image. If you are saving to an external 3.5 mechanical HDD that is only powered by the USB socket then the Hi10 Plus must be connected to an external PSU. The PSU should also be connected for the entire update process!
I made sure I had more than 10GB of free system drive space available (I actually had 17GB free). I made sure that sleep mode was totally disabled. I also disabled any third-party firewalls and virus scanners.
The whole process took 4 hours, but it went okay and everything appears to be working fine.