Are Demon and Dart seats different?

I'm not sure who really manufactured the covers. I got them from http://www.pgclassic.com/ . The auction link is http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&&item=120287675089 . If you click on the color choices, I got the 340 blue. I'm not sure if it's the same as the 340 blue Legendary uses or not. I'm not sure what that grain is, but maybe you can tell from the picture?

I am hoping to add about three enches to the front and rear of that piece, so I basically need about 6' x 6". I'd imagine that normally you'd buy two yards of fabric to do that, right?