There is but one small reference to it (and a drawing) in Peter Rowledge's oul book on the Maunsell Moguls. I think the author made the point that such an engine would have been somewhat heavier than the Woolwiches, which would have led to some concerns about axle loadings, etc.
GSR/CIE were always short of money, and expenditure on something like this would not have been forthcoming anyway, particularly if there was an alternative in the form of diesels.