Well into February already - crikey. Time flies! We received the flex cables - shown below with a 16 pin DIP package for scale :

Quite small! The flex is 0.15mm thickness and is hard gold plated. Since an IC pin is roughly 0.25mm(ish) in thickness, the socket stretch is very minimal with both the flex pin and the IC pin installed. Their arrival meant we could assemble a test board :

And this is how it installs in the IIc Plus. The ROMXc+ module inserts into the monitor ROM socket and the MMU-Link flex cable into pin 20 of the MMU socket :

The MMU is then re-installed on top :

Very happy with the flex cable length and placement - it was a bit experimental (it was mocked up with a paper template to get the sizing correct before laying it out as a flex PCB), but seems to work well so far. Now we can finalise the CPLD code and flesh out the stock flash image for the ROMXc+ - it will of course contain the stock ROM image along with Michael Guidero's ROM 5X plus various game/DOS/utility images as per ROMXe and ROMXc.