This week I picked up the Lionel 6-81749 Pullman Baby Madison 3-Car Set from Grzyboski's Train Store. Since the older 4-car Baby Madison set 6-81749 is rated for O-27 curves and from what I could dig up on various train forums, I assumed/hoped that this 3-car set would work on my O-27 layout, despite being rated for O-31.
When my purchase arrived, I was a little disappointed, but not disheartened, to discover that they derailed on curves. However, when I removed the coupler-end wheel set from the 6-wheel trucks, the cars ran fine. (I did not have to remove wheels from the tail-end of the observation car or the head-end of the combine, the latter of which is coupled to either an non-passenger car or the tender.)
I picked up some postwar axles and flange-less Madison wheels from the Train Tender, and when they arrived today, after a little bit of filing to shorten the axles, I was able to easily install them in the trucks. Much to my delight, they work as I had hoped.