Dear jimc,
best would be to have the HP41CX with internal X-Functions and Time module. Expand the internal X-Memory by one or two plug in X-Memory module or better by an Double-X-Memory module. Next install the CCD module. Than install HP-IL module plus EXT-I/O for interfacing to external world :
Use the full version of EMU41 on your PC : This replaces some real IL devices (mass storage, printer, barcode print, video screen). Furthermore you get an advanced emulator and a gateway to PC-world and exchange by internet...
Therefore the best today HP41 system solution is :
HP41CX
Double-X-Memory
CCD
EXT-I/O
EMU41 (advanced emulator, mass storage, printer, barcode, video screen, gateway to PC and web...)
For HP41 interface applications to real world and for measurement data logger applications take the HP82166A IL-Converter and I/O-Board or IL2000 System ...
Best wishes from Germany - Christoph Klug