I don't think the 0 KG load will be anything of concern since the iQ roof rack grabs onto the frame. and the roof rack is obviously a few inches above the roof. Lets just hope no one puts one of those roof top carrier bags on the roof with a lot of weight and messed up the roof lol. I've seen it happen before on another car.thule made one for the Toyota iQ. They uses the gutterless mounting kit. Guess it grabs onto the frame by the door opening. max load is 50kg.
On a side note, Toyota have a maximum of 0 (zero) kg load on the roof.