I'd want something that can expand and contract with the wood. It moves WAY more than metal so a top coat that is unable to move is going to fail.
I don't think CC would 'soak in' any better than spar varnish would.
I agree the spar varnish is only good for a year or so (left out doors) but always wind up asking Why Clear? It's not Stock/original and it doesn't last long. A Black semi transparent stain would sure be easier to redo and keep looking good IMHO. At least it will soak in. If you really want natural looking wood go with turpentine/diesel/fresh motor oil like the old timers did...
