I've seen and gone through that guide before, cheers man. It didnt mention that the shoulder belts should not run straight accross the shoulder. The idea is that if the shoulder belt is resting on the driver's shoulder, in a crash it will push down on the shoulders and could compress the driver's spine. This is why it should run accross the seat and then down towards the shoulders pulling the driver back into the seat (as opposed to pushing down on the driver).
Why do you say its better for the strap to rest on the driver's shoulders?
Cheers for the input