Arko,

Maybe I'm not understanding you. The diagram of the gunwales is very explicit and shows a curve in both the top and bottom of the gunwales. Layout the gunwales as per the diagram (plot and fair the curves) and remove the waste on both the top and bottom surfaces. It appears that each vertical line is 3".

I am not very familiar with this particular kayak but shaped gunwales are common in arctic kayaks. Most Greenland kayaks, however, have only the upper surface shaped.

Greg Stamer