This is my setup with a WhiteCat51, which is essentially the same as a RecCat51, except that it is white, not red.
I designed and 3D-printed my own autofocuser for it and I am driving it with MyFocuserPro loaded on an Arduino.
Works like a charm! Total cost of all materials: ~$ 40 plus an afternoon of soldering.
If anyone is interested, I would be happy to share the 3D STL files so you can build one yourself.
I think this design is superior, because it does not use a belt drive. There is virtually zero backlash in the setup.
And the focus it achieves every time is perfect! Look at the V-curve in the screenshot.