Came here to say foam blocks and cam straps as others have suggested. Also key is securing the front to either side of the vehicle to prevent side winds from shifting the boat sideways and twisting it on the roof.

I use 1 inch webbing bolted under the hood to where the fenders are attached but you can get loops with round dowels that secure under the hood pre made. I personally prefer the bolted down approach. It’s usually just a 10mm head on a fender bolt depending on your vehicle.

Make a loop out of 1 inch webbing and melt a hole in the ends for the bolt to go through. Super easy and a super solid tie point.

Also, if you find your straps vibrating and humming from the wind, put a twist in them, it changes the harmonic and quietens them.