I added the ute load leaf to the bottom of my sedan pack, then flipped the 2nd from Bottom onto top.
In a ute you have 4 leaves sedan only 3. No need to add a leaf in ute.
The jiggly nature will be the empty tray skipping around.
Also new shocks if not suited for shortened ride height wont be doing too much as the won't have full travel.

It's not the best solution but IMHO it rides better than blocks in my car as I wanted lower but stiffer due to towing a trailer some times.