I have used for years T-Max 400 film from 35 mm to 8x10. I use T-Max RS Developer and pour the small bottle into the larger one. I also use the JOBO CPP2 processor. As for a general dilution I use 75ml of dev. to make 1000 ml of working solution and a 5 minute Dev. time. at 70 degrees. I also give all negative one minute Pre-Soak but I have been told it should be longer. Most of my smaller negatives come out perfect. But in a few large format negative I get this vertical mottling or streaking in the clear areas of the sky. Some areas where I took these photos from I can't go back there. I want to prevent this happening in the future. Would it be T-Max RS or is there a MUCH better developer for T-Max films? Any help would be very much appreciated.