Looking and sounding good Fred. I can't help with the steam dome top. Yes, they just pull loose and get lost. I thought perhaps an Annie steam dome with the top cut off could be modified to suit but the top bit is a much larger diameter.
George. If you can fit, the Bachmann Climax are available for a reasonable price. Not exactly small but not so big either. It's a perfect logger and has the right visual wizzy things you need.
With a short skeleton log car, there would not be much clear track left in the display for the size you gave. Perhaps just enough though.