Bit unsure if this is the good location. Anyway, I have been looking at videos of Cape York and also some fail videos. I came across this video ( https://youtu.be/NCWQ0ihnQAM) and some photos of roof racks slidding off.

Looking at my own full length roof rack with tent, jerry cans, kayak holder and kayak, I am aware I am pushing the limits.
Did anybody secure there roof rack with extra safety measures besides the standard clambs?

Things I can think of, is filling the gutter just before and after the clambs with some metal, drilling a hole through the gutter and bolt/nut it up.