3. With the DDRS, as the rear is unloaded, the front is also unloaded so the car stays flatter. Under braking the rear DRS will close and the rear will start to generate downforce again before the front does (because of the finite time it takes for the system to "talk" to the front wing). Thus as the driver hits the brakes the nose dips slightly but the front wing is still in "low down-force" mode so it doesn't dip fully. As the front wing comes back in to "downforce" mode, the car's speed is already dropping (about 0.5seconds after hitting the brakes but that's enough to have dropped the speed a bit in these cars) so the dip isn't as big as it would normally be - the ride height change is less.
I question plank wear is ever an issue on most straights. From discussions about the 'see saw' splitter is seemed to be the consensus was that plank wear came from track irregularities, curbs. etc.
I also wonder how much forward weight transfer there is under braking compared to the loss of down-force from the DRS. I have a number for the DRS flap down-force, but need to calculate the weight transfer. What is the Braking G load and the estimated CG of the cars?