: Generally, but not always, a larger person will have larger hips, and perhaps
: larger hands, which will translate into a wider beam if you use the
: "hips plus a fist on each side measurement". Also, when fitting
: the curved deck beams to the shape of your body (for a SOF), larger legs
: would require more clearance and curvature of the beams, which would
: increase the volume. Within reason, the anthropometric measurements will
: get you in the ballpark. Perhaps the anthropometrics should be amended for
: modern times to say add a fist to either the side of your hips or the
: front and back of your beer-gut, whichever is largest ;^)

I don't think hand size or hip width is weight dependant. There are heavy people with narrow hips and light people with large hands. Sure, as a rule larger people will have larger hands and hips, but it is a rule with a huge amount of variance. Weighing yourself is so easy that I am not sure why you would want to try to use your hands as an estimate for your weight. It just seems kind of silly. If you want to know how much displacement your kayak needs, hop on a scale and you will know. It is extremely accurate. Yes, it is hard to calculate the volume of a kayak, but it can be done with excellent accuracy.

I certainly don't advocate ignoring the width of your hips and length of your legs. Obviously, they are important for a good fit. but use your hip width to determine the fit of your hips. If you want more width then add enough to satisfy your needs. If this happens to be similar to your fist width, then that is a good measurement. 4 inches, 10 centimeters, one hand width, whatever they are all arbitrary units. But I don't think there is any useful correlation between hand width and boat performance.

Luckily it is hard to design a really bad kayak so using a system that works for someone else will probably result in a decent boat for you. Anyone starting out in kayaking will have to make some arbitrary decisions based on little experience and choose a boat. Choosing dimensions of a kayak based on a system developed by some folks in Greenland will probably produce a better boat than average if you want to do paddling similar to those Greenlanders. If you are lucky it will be perfect, but be prepared to make some changes on your next boat.