This refers back to discussion of the FINECAST W class kit back on the first few pages of this thread and issues over accuracy of the kit based on the box photo. My father as a young man started to build a live steam model of the SR W and procured a blueprint from Southern Railway dated April 1937. He never got very far. But the drawing may be of interest.
Here are the drawing and a version with the FINECAST photo alongside. It seems to me that the main disrepancies are
1/ the FINECAST rear bogie has too short a wheelbase
2/ The chimney on the drawing is wider
3/ The FINECAST picture shows the dome and whistle too far forwards
4/ The FINECAST footplate drops in level above the cylinders in the wrong place.
However these discrepancies are in part evident on the box photo only, and not on the actual castings.
Comparing the castings to the drawing scaled to 4mm/ft the footplate level drop is in the right place, and so is the dome position.
The cast bogie wheel base is wrong however. It measures about 23 mm which is a mm short of the correct 6ft dimension, and I can easily believe that chimneys change shape over the years.
I am happy to supply a high res scan of the blueprint on request.
Also here is a photo of one of the early proyotypes from "British Locomotives Illustrated", by W.J. Bell, published by A & C Black of London, 1933