Kevin12 -- I eventually 'solved' the noise issue by just removing the replaceable spring altogether. The bike rides quietly now, and since most of my miles are on fairly smooth roads, I don't really need the full damping. When I do ride on rougher roads, the Roubaix is still much nicer than the Secteur I used before.
The Secteur (2010) is now my wet weather bike. The Roubaix has never been ridden in the rain, or had water anywhere near the FS components. I still think it's sub-par engineering, but I'm basically happy with the bike, especially since I switched out the wheels for tubeless and Conti 5000 TL tires. That change, plus the FS, makes the bike very nice to ride.