I routinely carry inflatable boards on my roof rack. They are Fanatic and like the Red have a high PSI, I would think Niash would be exactly the same all being high quality inflatables. I would hope most other brands would be fine so you should be good.
I'm no science talking guy but in my opinion, an inflatable would be MORE capable of withstanding the forces of wind and air resistance when travelling at 100 km/h than a solid board.
PTWoody said.. I'm no science talking guy but in my opinion, an inflatable would be MORE capable of withstanding the forces of wind and air resistance when travelling at 100 km/h than a solid board.