I am getting mixed messages about putting roof rail On my new MP. The owner manual says that it will take 50 kg and Mercedes have confirmed that. Thule seem to be the only manufacturer that fit to the T channel system that is fitted to my MP. Yet they will not recommend any system for the vehicle with a pop top. I am also reading in forum that people have experienced cracked roofs. Therefore it feels like it might be dangerous to put a roof bar system on my vehicle to carry three surfboards. Has anyone got Experience and views with regard to this problem. I seem to be going around in circles with Mercedes and suppliers. Thank you