I got 94 in 2U last year and I usually finished the old format in about 2 hours. You generally need a high-70% to get Band 6 and so, I expect ~82% for a 2U Band 6 this year. I used to consistently get ~115/120 in trials and HSC papers.
To be honest, most Band 6 students in 2U should be able to complete the exam with ease.
Also, the Band 6 cut-off is standards based. In theory, if they set the cut-off to be 90/100 and everyone got over 90, everyone would get a Band 6. The reason why the same cut-offs are set every year and roughly the same percentage of students get Band 6 each year is because the tests are relatively equal in difficulty and each cohort is about the same level as a whole.