To anyone who wants to know some laptimes for their practicing, I just got a 1:18.613 in GP mode (qualifying session). I also had another go at time-trial; I managed to slightly improve my time (the McLaren one) to a 1:17.617.
A surprising amount of time time can be won or lost in the last sector, a clean line though ascari and a nice exit out of the parabolica are crucial for a good laptime! I also had a go messing around with the camber angles of my setup, it seemed to make very little difference to my laptimes (half a tenth either way). Tyres seemed to go off at the same rate no matter the camber angle as well for me in GP mode.