BigShrimpin,
Cooler bag yes. Grunden maybe but probably be better as chaps or apron because the flex is minimal. It would bind up and not be very comfortable at any joint (knees ,waist ,etc)
You could use it for an enclosure but I wouldn't. It would be to thick to complete the hems where the top panels would come together. When you sew a top together you have a top panel,front flap and pocket (for bimini frame) in one seam and it would be hard to get it to fold flat (sewn first underside and then top sewn). Not to mention there won't be much (if any) stretch to complete any curves in the top.
Another concern would be how waterproof it would be at sewn seams. Even with seam tape a number 20 needles leaves a big hole in vinyl.
You could use it place of Weblon/Stamoid vertically in a fly bridge enclosure say to frame clear vinyl but remember the billboard vinyl isn't clean. It has markings and imperfections.
If you were using it in a commercial applications like making wings for a CC it could be used but it wouldn't be pretty but it would keep you dry.
I'm using the billboard vinyl to replace rip stop material that I used to make blanks for my fly bridge. Needless to say the cheap rip stop just torn all up after a few months. I used the blanks in the fall and spring while getting things ready for winter/summer.
