OK, revision number 2!
In a comment on AJay's video, someone says they successfully use an HDMI "dummy plug" instead of a dongle/adaptor to fool their PC into thinking they have an HDMI monitor plugged in.
A little bit of googling suggests this might work without requiring my specific setup with one monitor acting like two monitors. They seem to be very cheap (£3.75 on Amazon here in the UK for a device that 'pretends' to be a 1920x1080 monitor and claims to be OSX compatible). If you have a spare HDMI out on your Mac that may be all you need. Otherwise you'll need a USB to HDMI dongle + dummy plug. I'm going to buy one and will report back in a few days whether it works or not!
In a comment on AJay's video, someone says they successfully use an HDMI "dummy plug" instead of a dongle/adaptor to fool their PC into thinking they have an HDMI monitor plugged in.
A little bit of googling suggests this might work without requiring my specific setup with one monitor acting like two monitors. They seem to be very cheap (£3.75 on Amazon here in the UK for a device that 'pretends' to be a 1920x1080 monitor and claims to be OSX compatible). If you have a spare HDMI out on your Mac that may be all you need. Otherwise you'll need a USB to HDMI dongle + dummy plug. I'm going to buy one and will report back in a few days whether it works or not!