(from this topic:
http://www.e90post.com/forums/showthread.php?t=690972)
Back when I did this, I got a 3' x 5' sheet, but didn't specify which way I wanted it cut...so of course, it was running the other way! But that still let me do everything except the longest piece, and for that I ordered a second sheet, 1' x 5'. For what it's worth, I got mine from Auto Vinyl Solutions, and for the second order, they cut it the way I requested.