Hello Martin
We have recommended for years to stop using STOP BATH, especially when using Clayton fixers. Most acid, rapid fixers are buffered against the alkalinity of developer carry over. The sequence of develop, fix, rinse is how processors are set up. You won't "kill off" the fixer rapidly. You always can replenish the tray with fresh working strength fixer as you go along. You don't even have to waste your life rinsing between trays.