Nice work on those stock car doors, LASM, and the timber as well... I will make a note of those ideas.
On the subject of alternative materials, a completely useless idea that I was, nonetheless, very proud of when I figured it out a long... long... time ago...
Back when I was a teenager, I made a water tower from plans published in RMC. It was a very unconventional water tower -- a brick base, and a very narrow, metal tank.
Believe it or not... the cardboard tube wrapped around... ummm... one of my older sister's 'monthly supplies' .... was exactly the right diameter to fit the water tower tank. I kid you not.
I fished the tube out of the trash (understand it was perfectly clean, the tube was removed before the product it held was put to use...), trimmed it to the proper height following the plan, and then built the base using cardstock and brick paper.
As for the metal for the tank... I knew aluminum foil wouldn't work. But one night we had Shake - N -Bake for chicken. In those days, the seasoning came in a packet that had a plasticized foil interior. It was ideal -- metallic, but not "crinkly" like foil. So I took the now-empty seasoning packet -- which was large enough for the job -- and carefully wiped off any remaining crumbs of seasoning from it. (There weren't many because the way it was made, the seasoning didn't stick to it.)
I wrapped it around the tube, cut a piece to fit the top, trimmed it to size, then took it back off so I could poke it from the underside to simulate rivets. Once that was done, I glued it to the tube, and the job was done. (The prototype used a separate standpipe, I think, but I honestly might not have ever finished that part.)
Anyhow, that is long gone, long with all the other stuff I made in those days...
If this helps someone on their model railroad project I'll be completely stunned...