Thxtech

The top button on the KD will control the load prior to programming. The KA will work as well. The CK however, must be programmed and have an active controller on site to function as a 3 way or keypad.

Here's another option. Instead of using the KA as the dumb end of the three way with the yellow messenger wire to traveler back to the KD120, use the CK and send power to it from the KD on that wire. You won't need the yellow communication wire at either end, and can use the traveler to power the CK. Then, the programmer tells the CK that it's top button is to control the load (KD), and he's got more keypad. Or, tell the CK it's a single rocker just to control that load. And as a bonus, you can now have status leds and back lit engraving like every other switch in the house. If cost were no object I'd never use a KA. Lots of options really.