I decided to go with the Fantastic covers. It was very easy - 1/2 hour to install 3 covers. The small amount of caulk that is removed does not effect the sealing of the vent. A little goop in the screw hole / edge of vent / install the brackets / and then a little goop on the top off the new screw.
1971 20ft fireball (too small)
1987 27ft Tioga (bad brakes / tires)
1998 36ft Discovery (rattles / air leaks)
2005 37ft Monaco Knight (lemon Lawed)
2008 40ft Monaco Diplomat (too big)
2016 Forester 3011 (ordered June 8th - Born Aug 6) IT'S HERE