All but three months later...
After extracting the three central scenic boards (created so as to fit in with my loft layout as well as eventually occupying centre-stage in my attempt at a portable layout) I was able to get on with the beginnings of the additional outer two scenic boards that will complete the "viewing side". As the earlier three boards form a curved whole, with no line of symmetry, I had to take some care with the shaping of the outer two boards. I wanted their shapes to be almost mirror-images of one another, so that they could be packed top-to-top for transportation. I also wanted them both to bring the overall curve of the layout round to exactly 90 degrees to its front, ready to join up later to some simple, symmetrical fiddle-yard boards. My original one-eighth scale plan indicated that it could be done, but getting it right full-size involved a fair amount of preliminary production of templates on spare wallpaper, then trial, error and adjustment in wooden form.
Anyway, having made those two boards, laid and ballasted track on them, made provision for wiring up, created some basic land-form and added (in basic mock-up form) a couple of road bridges and twin tunnel portals, I became keen to find out whether the layout would actually work in roundy-roundy form. I couldn't provide the intended final form of the fiddle yard immediately, as that would have involved building four more curved boards, shortening two straight ones previously used on another project, laying a load of track properly (twelve roads in all, including twenty suitably custom-curved points, with remote control), wiring up, and so on. I realised that Instead of embarking on all that work before getting any proof of the viability of what I'd already built, I could fairly quickly create a temporary "slimline" version of the final layout, using two existing straight baseboards unaltered, a couple of pieces of plywood sheet with simple bracing added, eight manually controlled points and no additional wiring. This narrow version of the layout would also fit in our single garage for the necessary trial running sessions too. It had to be done, so some quick basic woodwork and track laying followed...
In consequence of the very unpredictable weather of late, I briefly took over one room of our house this morning so that I could test-assemble the slim-line layout, simply to demonstrate at this stage that all of the boards will actually join up as intended, so that I can now complete the track where the fiddle yard approach curves (currently undesirable 2 foot radii) have to meet up with the scenic sections.
The rough, temporary, slimline fiddle yard:
Setting out ready for action, after evicting a couple of armchairs. Madame out shopping.
It all fits!
A slightly different view - as far back as I could stand without dematerialising to pass through the wall...
View from the other end, only possible looking in through the window, hence poorer image.
Creature comforts reinstated.
Stowed, pending the completion of the missing track-ends and a suitable opportunity to reassemble and do some serious test running, in the garage if necessary, while the "Summer" lasts.