It's YOUR loco, and parts aren't expensive. I would start by ordering the correct part. Then you can modify the one you have as much as you want. If it doesn't work out you can use the correct part put it back to stock. This loco isn't a rare collectible, so anything you do to make it run better is fair game.
I had a 2-4-2 growing up, and as Mr. Moran said, they can be derailment-prone when backing through Lionel O27 switches. In "real life" sometimes train crews included an extra freight car as a "handle" to reach in, and avoid backing a locomotive into a siding to pick up a car. If you can find a Marx switch, the type where the whole assembly swivels, it might work better with this particular loco. My $.02.