Have to agree with Hez.. if you raise pressure for qually it will be to get heat into the tires quicker, e.g. on your outlap so the flying lap you should be good to go hard.
To add to increasing tyre pressure for qual, when on my outlap, I am usually on and off the gas pretty hard, not only to try to get heat into the rears, but bring the brakes up to temp also, so on that flying lap when you throw out the anchor at T1, you can feel confident your brakes will work. Am not sure if brake temp affects tires in rF, but I have watched the GT3 porsche guys here do it to get heat into the tires too.
I once tried to use the same theory as initially posted "I thought that lower pressures gave you a larger 'footprint' for the tyre... which to my mind would be advantageous...." so tried it in a Kart on a practise day for an enduro. I had no grip and the kart slipped off the track and rolled...wont ever do that again.