I discussed a similar project with a buddy of mine. Neither one of us have the engineering background to know the answers to some questions. Primarily one of which was about the bars resting on the top of the bed vs requiring a frame. Our thought was to make mounted rails on the top of the bed with removable cross beams to support 2 stand ups. We were not sure if the bed could support 1000 lbs or more on the top or it a frame that distributed the weight to the bottom of the bed was mandatory.
This I am very interested in.
The method I had considered for loading was this. Harbor freight used to sell these for $250 but now they are only available elsewhere for over $500. I thought I could have a mount welded to the lift deck so the beach stand could be secured on the deck, then the ski on the stand is slid onto the rack. The stand then removed for traveling.