Success!
The Model 1 is reporting 48k memory without a DRAM in sight. Only two solder wires required, plus adjustments to the two sets of jumper pads which I have replaced with DIP switches for ease of testing.
I’m still working on the solder-less 16k upgrade. May not be possible. Will look at this tomorrow (maybe).
Two minor issues with the board. Seems I can demux 14 bit DRAM addresses but have forgotten how NOR gates work.
Also had to rewire the keyboard cable as the janky job performed by the previous owner died when I opened the case.
I’ve also 3D printed some replacements for the rubber-ish board standoffs that crumbled to dust when I flattened the boards. If anyone wants the files, let me know.