I have achieved some success since my self inflicted RTC issue.

I built a new eZ80 CPU module paired with a newly designed Bus interface module.  The new interface module has solved some critical compatibility issues I was having.

I seem to be getting better at hand soldering the SMD component.  The eZ80 pins are quite tiny - and my hands do shake quite a bit - but I got there.

Some images of the assembly

I start by assembling the CPU module, soldering all the SMD components first.  The resistors and capacitors are easy.  The eZ80 is a little tricky.  Once its done, I double check I don't have any shorts.

As the PCB pins are quite small, I use the interface PCB to align a few pin.

Then I can insert the CPU module and solder them.  Repeating this for a small set of pins, until all are done.

And the underside of the module, with all the pins finally soldered.  Only need to solder the ZDI 6 pin header.

The completed solution - ready for testing.