You will have no problem.
Here's some onfo on my set up..
www.seabreeze.com.au/forums/Stand-Up-Paddle/SUP/My-car-board-support-thingie/I often don't use it without a problem but it helps to use it for those days when I have 3-4 14' boards on the roof.. I also use it when I carry my 17' Glide.. 12'6" and under I tend not to need it.
I recomend using foam pads or blocks between the board and the roof racks.. and never tighten your straps too tight.. It's best to have to board wobble around a bit than risk damaging the board from too tight straps.
Check this out about roof rack pads..
www.seabreeze.com.au/forums/Stand-Up-Paddle/SUP/SUP-roof-rack-pads/?SearchTerms=How,to,make,roof,rack,padsDJ