Well, I think there is another way, but in that way you can not use the shape generator,size and other pan-tilt related features anymore on that fixture.
You will have to use *ordinary* chases to control them.
(re)Build a new personality, using the personality builder.
Use two custom channels for pan and tilt, name them custom x and custom y, for example.
Then use an attribute action with an dmx input to control them.