Loaded the car on the trailer and setup one of the corner weight scales to check tongue weight and determine the correct position of the car for about 500 lbs on the tongue.

With the car on the trailer as I towed last time, the tongue weight was 780 lbs.
Moving the car back on the trailer, I got the weight down to 530 lbs.
Looking at the tow rig with trailer and car, the rear of the Tahoe does not sag too much. The tools, spares and other equipment that are put in the back of Tahoe for race weekends, must be the source for most of the sag (Tahoe was empty for the tongue weight check).