For racing sailors that have been using products like Baltoplate, and VC paints, (hard racing finishes with not so great anti-fouling properties), you should take a look at the Petit VIVID line. I've been using Baltoplate for years, because it's alleged to be the best racing finish, and because I don't want to have to remove it to start with something else.
Just do a decent rough sanding on the Baltoplate, and put on the a few coats of the Petit. It seems to adhere just fine to left over vinyl paints with just a decent prep.
It's not quite as hard as these other paints, and it's requires a little more care to make it go on smoothly. Anti-fouling properties are better, and if you use the white color, it makes it much easier to do 'in water' bottom cleaning, which all racing sailors, inevitably, have to do. Very happy with this product and I know of many others who share this view.http://www.pettitpaint.com/