Two etched brass sheets are supplied with the tumblhomes already formed. This is most useful due to the fact that the body has to be folded up from one piece. Origami in brass springs to mind but , knowing Allen's etching, and that Bob Brown has already made one, I am confident that construction will be fairly straight forward.
This one will be powered by a Halling motorised bogie. I know that the wheels are small but am sure this can be disguised when fitting the bogie sides. These are from the 3mm Society Shop and are correct castings.