I'm pretty sure I tested it this way and the top can still move up and down. Maybe that's supposed to be ok since the whole bundle is bouncing together, but I didn't like it. I like adding the big straps in the back around the back window bar.Looking in manual it seems its a required step to use straps to secure top:
This explains why it bounces and rattles unacceptably, going to try this tomorrow. I expect seat belts to flap, and kinds of wind stuff, I dotn expect the top to be bouncing around and rattling like crazy.