I spent some time today switching my Slot.It Challenge Nissan R89C from digital to analog, without affecting its digital capability. It really was a simple and relatively quick procedure. I disconnected the guide leads and taped them down on either side of the chassis near the guide and unsoldered the ferrite man from the motor, taping it to the now passive chip. I then soldered two leads to the motor and connected them to the guide flag. Simple job and simple also to re-convert to digital. Here's a pic:
