traveling long distances with a roof rack

Ok - this weekend I am going to be road tripping it (long weekend), bout 5 hour road trip to warmer waters to surf.
i have never owned a fiberglass surfboard (only my big plastic bic) and i know that fiberglass boards are delicate. i recently purchased a 6'4" glass board (pic in the shortboarders section). but anyways, my question is, i use soft racks on my car. would having it on the roof with those tight straps cinched around it for that long a ride, hwy driving with possible stones etc hitting it be that bad for the board? would it get pressure dents having the straps pulled tight around it?
it is a possibility to put the board in the car, but definitely an inconvenience if i dont have to - as there will be other people in my already small car.
thanks.
i have never owned a fiberglass surfboard (only my big plastic bic) and i know that fiberglass boards are delicate. i recently purchased a 6'4" glass board (pic in the shortboarders section). but anyways, my question is, i use soft racks on my car. would having it on the roof with those tight straps cinched around it for that long a ride, hwy driving with possible stones etc hitting it be that bad for the board? would it get pressure dents having the straps pulled tight around it?
it is a possibility to put the board in the car, but definitely an inconvenience if i dont have to - as there will be other people in my already small car.
thanks.