If you add about 20-30% by volume of Cabosil, it will be less likely to cause runs and drips. So fewer coats will be required. But that doesn't do a darn thing about the extra weight. The main problem here is getting enough pigment in the epoxy to make it opaque. And then it still needs UV protection.

A better solution for opaque white would be to use aliphatic polyurethane. It adheres extremely well to epoxy - in fact epoxy is the preferred primer. It goes on really thin, maybe .75-1.0 mil (.00075-.001"), is tough as nails, has excellent opacity, and supplies a great deal more UV protection than varnish. I painted the hull of a S&G with this in '95, and haven't needed to touch it up yet.

: I've been using white pigmented epoxy on paddle tips, but I don't think I use
: in on a boat, for one reason: weight. In order to get it to be opaque, you
: have to apply it quite thick, which would add considerable weight to the
: boat. You would also have to apply it in several thin coats, in order to
: avoid runs. Paint would be a lot lighter and easier to apply.

: Additionally, although the pigment should protect the inner layers from UV,
: the outer surface would still be subject to UV degredation unless you
: apply paint or varnish over it, adding more weight, expense and work. All
: in all, it seems like more hassle than it's worth.