After the transporter wagon cock-up I had to think slightly sideways for a moment. Several people emailed and suggested two things.
1. inside bearings for the bogies to reduce the amount of material outside the wheels.
2. fix the bogies solid and remove outside axles to run as a four wheeler.
Both these are useful ideas, and my thanks to the suggesters.
However I decided that the best thing to do was to start again with the transporter and turn the remains of the fail into a bogie flat wagon, of which more later.
A trip to Nigel's today and a look in his Wild Swan Ashover book threw up the following spec's for the transporters.
8' wide o/a
4'3" bogie w/b
9' bogie centres
Nigel's quick calculation showed that if No 2 above was followed the new fixed wheelbase would be 4'9". That ain't that long. And so therefore - bearing in mind that the wheels are largely hidden - that a longer, say 6', chassis with 4 wheels could be used.