couple questions, what type of vehicle and what does it have for roof hardware? Or just bare roof.
type of kayak , plastic, fiberglass, Kevlar ?
does your car have 4 corner attachment hooks or loops ? How far is your trip with the boats on the top of the car ?
when I rented from western and mec long time ago they just provided foam blocks. And then bow and stern lines and as in the photos straps inside the car. It works but every car door jam and window design can be different. Issues that I recall was the strap went in the window and most cars you couldn’t fully close window. As well strap had to be released to open door. Alternative was strap in the door jam but made it difficult to close door
in the links you have from western you have the suction cup cross bar. What was the plan to attach to that to hold the kayaks ?