My question is, would I have the same problem with Cetol coatings from mior
bumps or
abrasions against the rub strakes? In other words, does Cetol penetrate the
wood like oil or a
stain, or do layers of it create a solid skin, like varnish, which is more
easily damaged?


The answer is yes and no... Seriously, Cetol does penetrate the wood
somewhat, but not as much as stain, or as little as varnish. It is also more
flexible and will not crack as easily as varnish. Cetol is also much easier to
repair if you damage it: most of the time all you need to is light sanding and
fairing and apply a couple of new coats. So the answer to your question, IMHO,
is that while Cetol would serve you better than varnish, it is not perfect for
the application you have in mind. It would still be my choice since Cetol is
easier to apply and repair, but note that removing it (if you need to) is just
about the same as removing varnish.