In case it isn't clear to anyone the reason you need to buy "excess".
The pattern of the "channeled" vinyl is vertical on the finished coaming. The coaming needs approx 8" of fabric to wrap around..with the pattern vertical.
Wrapping three pieces of the coaming will total 24" (2 gunnels and the transom)
You only need 24" of "vertical" but you have to buy 54".
That pattern is sold at 54" of "vertical channel" and in horizontal increments of 1 yard.
If your gunnel pieces are like most boats, they are longer than 6 feet, so you always need 3 yards, unless you stitch pieces together
Basically, You have to buy enough to do the project twice. Thats not a bad thing. Maybe you make a mistake...maybe you ruin one piece with a treble hook in the first season and have to redo it....