i tried , but didn’t find anything other than a couple of articles from the 1981 and 1985 but they didn’t mention what scale they were so i assume HO (and i didn’t have either issue in my collection)
Used flat bottom HO brass rail is fine it just has to be reasonably straight ish
its wanted to go on top of the cross beams on a “G” scale log car two lengths per cross beam, in that size it equates to something like 14lb rail which would be correct for what its to be used for.
It’s function on a real car would be two fold one to reinforce the cross beam and two to make it easier to slide logs on and off the car.