Howdy - n00b here
I am just about done with FL-II myself, and i ate at about 500 cals under maintenance most of the time. From FLII combined with Alwyn's metabolic overdrive routine I've lost a great deal of body fat and gotten stronger all the same so i'd recommend this level (500 under) as a good guideline.
NROL (the original) didn't really specify how much to eat for fat loss, but this has worked for me. It was very hard not to go over with the cals, though. Eating lots of protein will help keep you satietated.