This may be bunk, but...
I had lowered my bunks to paint the hull (one side at a time, with straps and support beams to ensure stability), and after painting raised them to where they were when I bought the boat and trailer. Over time on the trailer (and familiarity with the boat) I noticed what I would call reverse sagging, or distortion at the keel, upward, so that the deck was raised at the sole plates. Recently I raised the bunks to their maximum to expose and remove the bed to that I could chip and treat the keel, putting the entire boat's weight on the bunks for over a week. During that time the keel gradually dropped less than an inch, and the distortion inside flattened out. So, when I reinstalled the bed, and lowered the bunks, I did so that much of the weight was still supported by the bunks (my goal was to support the keel with the bed, the hull weight with the bunks and keel, equally). It's been trailering well, and there's no distortion.