Thanks to all for the advice about the pickup rollers. I ended up mounting a few rollers from my parts bin underneath the flat. Since the loco gets its own AC- (by simply tying together the two sides electrically), it takes only one wire from the flat. An added benefit is that the engine could easily be converted back to 2 rail if desired.
She's running around very nicely, with virtually no trouble staying on my Ross track. You can see some of the other details I added, for example newly fabricated wooden doors for the cab, brake shoes and cylinders, sander and air lines, etc. The last photo shows it nose-to-nose with my customized Lionel 0-6-0T, for perspective. It was a fun project!
