My experience is mostly with tri-x and pyrocat. With fresh film - an hour stand is fine with 1:1:150. With old film, 36 minutes is fine but an hour has a LOT of base fog. I have not had high fog on FP4 either. With normal development times base fog with p'cat is very low - somewhere arount .15 usually for tri-x and .1 or less with FP4. J&C100 and APX100 is even less.