Well 1/35 is 8.709 mm = 1 foot, so OO gauge track has a gauge of 16.5mm, so it is about 2ft.
So I have been scratch building a coach in 1/35 scale on the lines of the Lynton & Barnstaple Railway.
Here it is undercoated, running on Hornby OO bogies, I still need to come up with a livery.
Completely out of card of various thicknesses.
It is about 1 ft long, I need a few more and a loco to pull them, then a model railway layout to run them on, it never stops!