while equally valid ( i hope ), an opposite way of looking at it would be to take the proportion of rise of 50% of the DWL from the baseline.

so in really rough terms if the waterline length was just over 16 feet(too bad a little more than most yaks), then 50% would be just over 8feet (100inches or so).

then if the rocker was 1" measured at this point, the dimensionless number would be also be 1%. so then using percentages to account for any length vessel, it is fairly readily transformed in our minds to a fairly typical boat length.

but it has some cons - usual measurment is taken (arbitrarily) closer to the ends than 25%dwl, and probably should be 50% around the cg not the ctr of the dwl, etc. too bad, but it speaks to me more than the usual.