Our take

Treat the aerodynamic claim as decoration. A soft bag has no fixed shape once it is loaded and moving, so it deforms into whatever the wind and your packing decide, and the fuel penalty of anything on the roof at motorway speed lands somewhere around ten to twenty-five percent regardless of the profile printed on the box. Judge this on price and seams instead, which is where it does well. Pack the flat, heavy items low and against the crossbars if you want any of that shape to hold.

Best for: Occasional holiday use where price matters more than refinement