This is the method I use but with a twist. I first spray the mold with epoxy primer (Klass Kote) and then lay up the 0.6 oz cloth. That pretty much assures a pinhole free, light, strong, and sandable base for a pristine finish. It's more work, but worth it to me.
I've only layed up one canopy with the cabosil method and it picked up too much weight for my taste.
MattK
ORIGINAL: davidfee
Ok, I see that you disagree with me. That's ok. I've tried a great many things, including what you suggested. I've found that using a layer of 0.6oz glass gives more repeatable results, with less weight gain. And it's adding fibers (strength) instead of just resin.
I like to make my layups pretty dry, as my goal is maximizing strength and stiffness, while minimizing weight. Cosmetics are also important. The layer of light glass works for me. I never said two ounce... I'm talking 0.6oz-1oz. I guess "very light cloth" is a relative term.
-David