I agree with the 90 minute prior to opening time. There are two conflicting factors. First, the early hour would typically deter many people allowing you to be arrive a bit later. However the holiday will bring many more people, all thinking the same thing. If you can get there no later than 90 minutes prior.
I arrived at Security 90 minutes prior to a 9am opening in early August and after waiting at Security, the tapstiles, and the rope I "walked on" FoP.
Wishing you success at rope drop!