We were there last week. Arrived 70 minutes before the park opened. Rode FoP at 8:45. Then went on Navi with a 10 minute wait.
At 9 am (park opening), FoP was 120 minutes and Navi was 60 minutes.
i agree that I would not wait more than about 15 minutes (its fun, amazing effects, but not that good).
If you want to ride Navi without a wait, you will need to be there before park opening, but not as early as FoP. FoP is where the majority of people arriving early are headed.