The new, slightly larger LCD panel has arrived, as has a PCIe riser plus mounting frame. Someone else warned me that multiple PCIe risers that he tried didn't work, a good reminder that everything should be tested...
The video above shows the test run using the new components. As you can see, it's all working well. Using a ready made graphics card mounting frame eliminates the need to design one myself, saving time.
I'm still waiting for the new battery pack (which is finally back in stock). Assuming that works as hoped, then I can move on to designing the case itself. A power board also needs to be designed to handle switching it on and off, because the off-the-shelf USB-C power sink board doesn't have all the circuitry needed to switch the machine on and off.