I process 2 8x10 negs in a unicolor drum that I roll around on the floor. I use the same set up for four 5x7 negatives. I use 500ml og pyrocat-hd at 2:2:100. I have not had any issues with the 5x7 negs as long as I get the dev in really fast and knock it over right away. With the 8x10 I am getting lines of different densities. I do nothing differently. Why?