GMAT Strategy

I have seen a couple of difficulty level breakdowns of question on OG 11 and I was wondering if there is something similar for OG 12?

After doing about 60% of OG 12 I realize that the majority of these questions fall in the easy/middle bins and I really need to practice with hard level questions. Any book suggestions?

Actually, all the guides have problems ranging from easy to difficult, so you should just practice the last 50 or so questions for each section to get the "hardest" questions.