In Gordon Hutchings "The Book of Pyro", Hutchings recommends the following starting times for FP4 (EI 80-100) Normal Development 10 minutes @ 70F N+1 13 minutes @ 70F N-1 8 minutes @ 70F (+1/3 stop exposure)(posted 9121 days ago)Hope this gives you a starting point, but seriously you really need to test your film and processing.
Mike