I should probably confess that the chassis has also seen a bit of work. This comes in three forms, a result of trial and errors.
1. The pony frame has been lengthened to ensure that it swings properly. That was fine until I realised that I’d put too much lead in the smokebox. Hence:
2. I have added a spring bearing on the top of the pony. That kept it on the rails, but didn’t do enough to stop the rear (driven, rigid) axle lifting on curves. So…
3. The tender was modified to bear on the back of the engine by removing the compensation beam and lightly springing the front two axles. This seems to work. The ghosts of messers Sharman and Rice might have smiled.
Adam