The following pics show how much you can file off the case before the sensor starts malfunctioning.
Height before: 4.55mm. Height after: 4.15mm
Thickness before: 3.6mm. Thickness after: 2.4mm
I kept filing it down:
At 3.9mm height, copper starts to show. Still working!
3.8mm: the copper tab is around 3.4x0.5mm in size. Still working. In this state it reacts instantly to temperature changes! Still working.
Height: 3.3mm. We're getting close...
3.3mm height, 4.5mm width, 2.4mm thick. Still working!
That's it. Our beloved sensor is dead now. The two shiny spots you see is the part of the actual die. It is located in the back of the case (where the case is rounded).
Sensor reads a steady 24°C at this point. No change whatever you do.
You could file off another 0.2mm off front and back to get to a final thickness of around 2mm. Your final sized down sensor would have the following dimensions:
Height: 3.4mm (to be safe), thickness: 2mm, width: 4.6mm