on the mvvs/evolution gas engines it is easy to adjust. A degree wheel is handy, but I often use a calibrated piston stop and time the initial spark at 0.1mm BTDC.
Adjustment can be made by removing one of the M2.5 screws that hold the sensor. Now the sensor can be rotated +- 5 degrees either side. It is not needed but for the experiments. I found a slightly earlier ignition timing reduced the tendency to rotate backward at very low idle speeds.