If you line up for project right when you are cutting it out, that is more than enough for a 12' ridgeline, I think it can be done with 8 or less if you plan right. But I always order at least a yard more than what I think is needed. most times I lose 6 inches on the ends just to make a flat side.
That and large scraps of sil are great for other spur of the moment diy ideas. Funny how fast the machine will come out when an idea geting in my head.
Is that too much to ask? Girls with frikkin' lasers on their heads?
The hanger formly known as "hammock engineer".