I'd be thinking hard about dropping off the car after hours. I've heard stories of people who have done that then been charged for damages they insist didn't exist at drop off, but car rental company insists damage was done.
If I had to do that, I'd probably pull up to the valet and video record the entire process being sure to include all around the car and keep the tape running even as the valet is driving away. Then I'd keep the tape.