You don't need a special roof rack for a surf ski. The traditional flat topped roof racks work fine with the ski fastened deck down.
If you have some cash to burn then get the Thule racks with the Hydroglide mounts, they hold the ski straight and apparently they help you to slide the ski onto the roof from the back of the car. Mounting the ski hull down has the advantage of minimising salty water dripping onto your car.
In SA the Holdfast range of racks are cheaper than the Thule and have worked fine for me for two years.
If you have some cash to burn then get the Thule racks with the Hydroglide mounts, they hold the ski straight and apparently they help you to slide the ski onto the roof from the back of the car. Mounting the ski hull down has the advantage of minimising salty water dripping onto your car.
In SA the Holdfast range of racks are cheaper than the Thule and have worked fine for me for two years.