Affixing ladders to Thule Roofrack bars

[traffman]

A good friend purchased the aero bars for his thule roofrack.
He seems concerned that all the clamps to hold the ladders down will not fit round the aero shape of the bar.
Does anyone have knowledge and or experience of what should fit?

Hope this is in the correct forum , many thanks in advance !

[Watchman]

Just open the hooks up in a vice.

[traffman]

Cheers.