Before I totally write this one off, a 3D sketch of Carter's Siding (yup, using pencil and paper!). This is not at all to scale or in proportion (the loading dock is too high - in model form I'd like it to be around 2"), but does help me in trying to visualise things. The bridge would have to have quite a hump too so as to clear the trains - hence the narrow gauge line darting off towards the backscene. It will probably never happen......