Small step forward but a large step back. The roof has been cut and bent, and will fit within lips formed by guttering mouldings mounted around the top of sides and ends.
However, something looked wrong after laying the items in place. The relationship between upper door slides and side guttering is wrong when compared with the drawing, either the door slide being too low and/ or the guttering too high by about 1mm.
Took a deep breath and removed the door slides plus attendant detail, then used coarse file to the body carcase to reduce the roof height slightly. With the slides propped in place slightly higher than before, the proportions look better so will start rebuilding later this week.
Herewith a quick photo before surgery, showing a mock up with roof nestling between rainstrip mouldings.