I attached a BOGA Grip, 260 Version, with an IGFA Certified Fish scale good to 60 lbs on the Tow Rope.

The GoPro was attached to the BOGA at an angle to film both the rider and the metered scale at the same time. On a crappy iPhone this is hard to read but its clear at full 1080P resolution.

You can see the drag for the Foil fluctuating between ~ 4 lbs up to 18 lbs. I pegged the average DRAG to be 12 lbs

The drag on the Surfboard from ~14 lbs to 30+ lbs - See next.