Thank you for your input, Eddie. The Moonie drawings are based upon the Dubbs engine LSWR 520/SR 3520/BR 30584.
I have photocopies of a very good article from the September 1977 issue of “Model Railways”. This has a drawing by the late J.N. Maskelyne and a photo of 520 in LSWR days with the larger trailing wheels and, you guessed it, 10 spokes.
I too have pictures of 30583 with 9 spoke trailing wheels but unless my eyes decieve me this locomotive seems to have retained the smaller size wheels even into BR days.
I suppose I could pick one of the many locos that were scrapped early in the century, rather than one of the Lyme Regis three and then work on the basis that nobody can say either way!
No problem with the 9 spoke bogie wheels and I have checked the driving and coupled wheels – both the latter correct at 18 spokes.