OK, I ended up cheating!

BOMBSHELL!

I've relented and gone down the easy road, for the time being, ending up buying a Da Vinci 1.0 3D printer about a month ago. To be clear, I haven't abandoned my main theme here, but over the last 12 months it's become apparent that, in the absence of other specialist machining (reductive manufacturing) devices, my project would end up either, being a bit crappy, or, take forever (=never) to complete. At my tender age I need to factor in life expectancy when looking at larger, complex projects such as this. I'm also somewhat of a perfectionist with high expectations and standards
for my own work.

So here's the new toy:

So far I've managed a couple of prints, but have clearly got a long way to go to get to a level of confidence I'll be happy with. Researching how to deal with some minor issues led me to a lot of material suggesting that, instead of the included printer (slicing) software, "XYZware", Slic3r or Cura warrant consideration to improve printout control and resultant quality. In the case of Slic3r I need to consider reflashing the printer's firmware, risking "bricking" the device, so that option's been eliminated, at least for the time being.

In order to establish where my real problem lay (either my Sketchup design method, or in fact the printer limitations) I decided to use an item from Thingiverse.com, a great repository of other people's 3D design and print output. My pick was MorenaP's Treefrog, which came out quite OK and certainly established that the printer and it's loaded software and attendant XYZware were up to the task, so clearly I needed to go back to my Sketchup drawing board and up my skills there.