The Cross Stops may be interchangeable, depending on how old your DF 500 is...
The current version of the Cross Stops, which is interchangeable between machines is marked on the end where the pin protrudes. One side says "DF500" and the opposite side says "DF700". If you have those markings, it is interchangeable. You simply flip the barrel over when you change machines. The pin is offset from center because the two machines are configured differently.
Tom