It seems like the later models should run smoothly at realistic speeds, since they have a “tight” worm gear drive. A long time ago someone advised me that they weren’t good pullers. Also, it’s hard to find examples with intact wheels. The pilot and trailing wheels especially seem to crumble from zinc pest.
I grew up with O27 trains, so I’m not a stickler for scale proportions. But the bodies are noticeably small for O-gauge track (they remind me of English trains), and I think they would look small next to traditional Lionel postwar and MPC rolling stock.
I don’t own any, and you’re right- I don’t know of any good reference books on Prewar Flyer.
