As rs2000 said you want your fan temp above thermostat. You onlt want your fan to kick in as you go over your normal operating temp otherwise you fan will always be on.
You need a little bit of leeway for the thermostat to cut in and out before triggering your fan.
I would suggest staying up around your 90's for your switch
 

Cheers Mate,
 
I am not sure when I'll do this but i'll try the 90 deg switch and go from there.
 
Cheers
 
Matt