As I said above I would retake photos of the shadow line of the backboard extension join. Here they are:
the line across the back of the layout
and on the left hand side:
as stated in the previous post, stripping the back scene off and filling and sanding the join with all the track work and wiring done and some of the scenery (the back wall of the large canopy and the canopy uprights) permanently in place is not something I wish to contemplate. I feel the mess caused could do permanent damage to the layout.
I have been thinking about non invasive solutions and I feel lowering the layout, should it ever go to an exhibition, By a few inches so that track height would be around 50 ins and deepening the fascia panel to about 41/2 -5inches would conceal the lines. With a fascia board that deep I could experiment with a row of LEDs on the bottom inside edge of the fascia slightly up-lighting the shadow and thus getting rid of it that way. it certainly seems to work with torches. Obviously at home, whilst a nuisance, operating the layout it is too high for me to notice.
Oh by the way Simon I have downloaded GIMP, I now have to learn to use it.!!!!!!!!!!!!!!!!!!!!!!!!!!!!