Old Cuben Spinnaker

Just guessing but…

North is a high end sail maker that pioneered cuben racing sails. They list an asymmetric 2A spnnaker here:  http://www.be.northsails.com/SailProducts/RacingSails/Downwind/VSeriesAsymmetricSpinnakers/tabid/4973/language/en-US/Default.aspx

Also, spinnakers are generally very big as they are a speciallized sail for running downwind. *IF* the material is something you want, and i have no idea if it is from the data you have, chances are you will get an enormous amount…like, you’ll probably never be able to use it all yourself for MYOG projects :)

I would also note that they are cut to billow. Seaming will not exactly match MYOG projects.
Used, it may leak, also. Hard to say, sometimes they get pretty good use.

Re: cut to billow.  Yes, but they are constructed of flat panels. It would have to be deconstructed and then obviously you would have to work with whatever the dimensions of those panels were.

re: leaking.  Also yes, obviously waterproofness is not the principal value of a sail :)