This topic has been a little quieter for the past four days!
I did not get to cut the bunker on Sunday, it was too cold in the garage, and Mrs G H Wood was standing guard over her kitchen table all day.
However revisiting some of the posts made, and following an exchange of pm's with several folk, and a detailed consultation with Bradypus, the conversion to a 2-6-2T, looks distinctly possible.
Nick has worked out the formula for the front pony truck, it should (just!) be possible to do this without adding an extension to the frames and running plate. Anchoring a frame stretcher in the area of the cylinders and hanging the truck from that. Having further studied Grahams photos in post #88 there seems to be the ideal mounting point for the rear truck where the battery compartment lid is fixed.
The plan would be to use two sets of Accucraft L&B wheels (25mm).
Rechargable batteries mounted in the side tank, with a charging socket disguised by one of either the sandbox lids or water filler covers, and the on/off switch in the rear bunker.
Anyone forsee any problems?