I started making some 9mm boolits, and I had the PID configured with 750F
I dipped one corner of the mold (aluminum) into the alloy
The mold heated up faster, actually cutting the sprue plate was very easy all the time, the boolits fell on their own with a slight tap.
A little frosties, but nothing that can't be solved with PC (it's an NLG mold)
I was making flux every 20 minutes or so and added a little tin to the mixture.
Is there a problem that you are not seeing with increasing the temperature?