Some say not to plug any fixture with a transformer into a dimmer box. But I've used the M260 connected to a DP415 (in switching mode) to turn on and off both an Agressor and a quad phase with no problems.
The M260 manual does not say use channel 264. It says that the Aux buttons use channels 261-264, e.g., Aux1 uses ch 261 and Aux4 uses channel 264. When an Aux button is on it sends out a 255 DMX signal (Full ON) on its assigned channel; and when the Aux button is off it sends out a 0 DMX signal (Full OFF).
So: (1) put your SP4 in switching mode, if possible (if it is not then dimming mode - although this might be riskier), and (2) set the DMX receive channel to 261.
Each Aux button will then turn on and off one of the four outlets.