Your best using separate bleach and fix. When I experimented with partial bleach bypass I found anything less than 60 sec to produce uneven negatives. Cut a roll up, shoot the same scene/s and process separately with various bleach times. I tried 60, 80, 110 secs plus full 6min 30. Print them all. Doesn’t take long and you should get to see various levels of bleaching. Think I found that by 110 secs it looked pretty much fully bleached.