Update: @
gtpcaine and @dano89, there is a rules provision which affects both of you.
There is now an official "footnote" on the car's specs which explains that all Ford drivers must use the same aero package (on a weekly basis, for clarification, as it may be altered from week to week) as deemed fit.
Since you already share setup details, I trust you can also include whether or not you plan on using the flat floor or not, for the slight handling advantage, or for the increased top speed.
I also recommend that everyone lowers the rear downforce a touch, if necessary/comfortable, in order to obtain a slightly higher top speed at Mt. Panorama. This has shown to make a huge difference in speeds coming down the mountain again, towards the Chase.
So, to summarize: Ford drivers can now officially use or remove the flat floors, if desired. All drivers must officially have the rear aero on their car, and all standard model cars must use any of the "generic" type wings. Downforce - as you already know - can and should be adjusted on these rear wings, to enable for a higher top speed or for more cornering stability, depending on driver preference, setup, and track.