I just picked up a cover for my 18SF on ebay and it fits awesome. also very heavy duty with a 5 year warranty. I am very happy with it.
here is the link. It will also work with high bow rails and standard center console windshield! Closest to custom fit you can get. I will post pics if you need to see it on my 18SF
http://www.ebay.com/itm/290709263893...84.m1497.l2649
-Fred