Thanks Gents. I had a different plan for the second side of the tracks but that now will become another build. More later on that.
So I trawled the web for a suitably sized WW1 artillery piece and found a 3-D printed Minenwerfer (25cm) mortar in 1/35th, thanks to Vargus Scale Models in California. Highly recommend them if this is the quality of the kits they produce.
Cleaned off the parts and put it together and painted it in about 4 days.
Currently painted with a little wear and a light coating of Alclad transparent smoke to dull down the colours. Still touch ups and weathering to do (like the Morser) and still decisions as to how muddy and messy to make the final scene. Then there are the figures! Slowly slowly……