The first thing we needed is a proper part for the sensor (thanks for the data sheet!), so I made one.
A3144 Hall Effect Sensor_.fzpz (6.7 KB)
It is on .05 in centers and 4.17mm wide.
Now we need to know the desired distance between the two red lines (i.e. the spacing between the hall effect sensors on the pcb) in inches or mm and we should be able to do this.
Peter