"I was told not to add extra epoxy to fill a weave. Because it adds weight and no extra strength. Instead, fill the weave with coats of varnish."

From my limited experience and reading, if the varnish is thin enough to go on smoothly, you will have to apply (and sand down) any number of varnish coats to equal the filling ability of a single, well-applied coat of epoxy.

The other issue to consider is that if you don't have an adequate filling of epoxy, it will be WAY too easy to accidently sand into the weave of the cloth. Sanding into the cloth will create a "fuzz" which appears "cloudy" or "milky" under subsequent coats of varnish.

To fill the weave on my CLC 17', I had to apply four thin coats of epoxy to get the weave on the 6 oz. cloth filled to my satisfaction. For more troublesome areas like the sides, it helped to prop the boat on edge so that the surfaces being worked on were roughly horizontal. (Less chance of the epoxy sagging or running.)