Is this fastrack? Does the switch have the 1/4 curve that's included with them from the factory? I think that completes the full curve but I could be wrong.
Actually the filler piece is a straight unfortunately. The curve if I remember for a O72 is complete BUT you cannot attach another curve directly to it because of the roadbed piece between the straight and curved portion so they provide a small straight piece to extend it out which kills the geometry of the curve. I'm pretty sure the O60s are the same.
I ended up taking a piece of O72 curve and cut the roadbed off to fit and didn't use the short filler piece. I'm not sure if this is what you are talking about but cutting the roadbed does work.
You can see the O72 with the cut roadbed. Can hardly notice.
Here the cut is a little more visible.