Re: USRA Twin Hopper car brake details
You can get a good idea of the B end detail from my book, pages 277, 288, and 299.
There's a USRA hopper at Steamtown and I took some underbody shots and also shots of the brake line, which runs down the side of the car, but I don't have any shots of the brake rigging other than the brake rod hanging between the two hoppers. I do have shots of the routing of the brake line at the A end of the car.
Unfortunately, brake lever badge plates weren't required until 1929, so the B end shots won't show them. That would have helped.
I believe there are drawings in the Pullman Standard collection in Harrisburg, but I wouldn't be able to get to them until after the holidays.