Years ago I had to transport a skin on frame about 500 miles for a friend. The bow and the stern needed to be tied down but the boat did not have any grab handles or places to secure the lines. I did have saddles and as you mentioned was a bit skeptical as to how the saddles will support the boat. So in rummaging around the garage to come up with a solution, there on the wall was my answer, my trusty old wooden ladder. Grabbed four large U bolts placed the ladder on top of my Thule cross bars, ran the U bolts thru the ladder and secured it with the plate on the underside of the cross bars. There was a small supply of pipe insulation that was cut to size and placed on the rungs near the center of the boat. Because of the rocker scraps of foam and a boat cushion were secured to the ladder at the bow and stern. Than VERY VERY carefully I secured the boat with many looser than normal tie straps to the ladder ( looser straps = more straps). Than was able to run the bow and stern lines to the end rungs of the ladder. This was not a pretty set up but after the trip, the ladder became a part of my Thule rack options. Haven't used it a lot but it has come in handy. This probably is not the answer to every day use but it worked for me.