The diagonals are an extra data point, you will succeed with out them or use them as a check.

Richard is correct in how to measure the dimensions. make sure that the point is 20 degrees below horizontal as shown in figure 4-2 of his book

> I have the primary offsets for Nick's Guillemot plugged into autocad but I
> can't figure out how the diagonal offsets work. So far everything I've
> tried produces a linear function. I haven't found the instructions on pp
> 49 and 50 of his book to be much help here. I'd like to get this worked
> out or I'll be paddling a box with a slight curve to the deck and hull and
> the craziest chines you've ever seen.