The 32' Adco also works on the Sunseeker 3170DS.  It is snug, which is good, the wind does not flap it around.  I used the same size on my previous 28' and it had about 2 feet extra on the front and back.  The wind would whip it around pretty good.  It only lasted about 3 years.  I expect it will last much longer on this RV. Even if it doesn't, I buy them when camping world runs a really good sale, and it averages out to be about $100 a year.  Completely worth it!  I don't even bother taping the corners or sharp edges. 
One of the things I do like about the ADCO cover is the vents near the roof.  I read that some of the other covers would cause the roof to mildew without them.  I have never had issues.