Towards the end of the Universal Mixing Video Part 4 Menno goes into detail about the auto generated ceiling and adjusting the elbow points and noise slopes. After auto generating I have been moving the elbow points to the primary, secondary and tertiary frequencies as needed and getting the slope readjusted. I'm not as much of a perfectionist as Menno is but I'm getting really good results, especially when sending the EQ'd sound into other plug-ins for processing.

I'm a new user but I believe when you choose a preset that is the ceiling curve that overwrites anything you auto generated. I've been auto generating and then adjusting the elbow points so I can capture and correct as close to the original sound as possible. However, I did use a preset for a Pop Grand Piano and it worked beautifully in the track.