The problem in GNav
Is simply that there are TOO many CRP 5 questions to do. 26 questions where you had to use the CRP5 were on the exam the month before.
Our instructor gave us paper after paper of questions where you had to use the CRP 5 and after 30 or so papers of it you do get a lot quicker, even if you yourself don't notice it.
One of my buddies failed his GNAV exam due to the lack of practice, he hadn't used his CRP 5 in weeks and thought he would be safe. (due to 26 questions involving CRP5)
Moral of the story> There's no such thing as enough practice.
Even if you think you know everything your CRP 5 can do, do it over and over.
Gnav IMO isn't as complex to me anymore since it's all about a few drawings, formulas. It's basically a lot like M&B, calculation after calculation, nothing to it. The trick may be though when do you know what formula you can use for what questions and what map i.e. POrigin, Convegence for the 4-5 maps (were there more?).