Yeah I took a few old R exams for my first practice exams and while they were long and not like the actual MCAT, when I took CBT 8-11 I found it much easier to stay focused the entire time due to the shorter sections. I also liked that the R had extra problems so I had more feedback about where my weaknesses were. Getting to the point where I was ready to take the practice exams was the worst bit, filling in the gaps at the end wasn't too bad. Felt like mental Whack-a-Mole haha.