So I have been talking to Ben at Chief Products, he’s been pretty helpful and I think I’ve got it all set up now.
I have worked out that you really need some planks (as chief call them) which pulls the whole thing together. I loosened all the bolts on the cross rails, installed the two chief planks and then tightened it all up.
It’s important to do this and start tightening the screws in the roof first, then he plank screws and after that all the bolts in the rails.
From my experience if you just try to install rails only they just dont sit right until there is a platform or planks installed at the same time. I didnt need the spacers when done this way.