[97XRAY]

The one time I went to a mechanic (porsche certified and been working on these cars since the beginning ~20years) I asked him this question as well; my car also runs between number two and sometimes slightly over number three.
On that little trip to the mechanic I ended up getting a thermostat - but not because the engine ran too hot, it was just not working to kick in the big fan. He measured and monitored the actual engine temp and said that the 2 and 3 marks are absolutely fine, though the fans should both be on once the car gets to the third mark.
Low temp thermostats can be used - I think there was a nice write up on that on this board a couple of years back, try searching for low temp thermo or something like that.
Good luck