Thanks to everyone for their inputs.
The car I was specifically wanting to model is the NYC&HR double-deck
stock car in the MR, Feb. 1959 issue. The upper deck boards run across
the car, not length-wise, and probably had center, vertical supports,
and a lenthgwise 4"X6" timber down the middle.(?)
At this time-era, I would suppose that center-post supports would be
The NYC&HR car looks like a permanent double-deck car.
I've seen that (of course) many different methods of support were used.
The Wikipedia diagram I mentioned, patent 106887, (c.1870), turns out
not to be a double-deck support method. I downloaded the patent
at, "Freepatentsonline", and it was instead a way of standing each
cattle across the car & separating & supporting them with vertical
posts, with a feeding trough at their head-end. Very interesting.
Thanks, Paul Hillman