I had a custom boat cover made from Sunbrella. It performed well, but I did notice some stretch.
Also, I was told Top Gun is probably the toughest, but its very abrasive and can sratch the side of your boat. Just someones opinion.
Current: 2009 X-Star, Indmar 6L, 400hp, ZFT3 tower.
2009 Moomba LSV
2009 Moomba Outback V
2008 Monterey FS180
Pelican 4 set paddle boat
plastic tug boat when I was 4