> The builders had tried to use cabosil as a filler for fairing
> and they went on to other things as the boat was about unsandable.

That's the only compound I used in building my boat. True, one gets to go through prodegious amounts of sand paper, but it definately sands down. Faired out the areas of my S&G just fine. Sharp sand paper does wonders, even with a random palm sander.