What do you use to clean the rubber parts on your arch and side rails?
For the actual cleaning, I use a cleaner called Vim. Simple garden variety cleaner but is has a very mild abrasive in it. Same for the the vinyl on the FG arch. For really bad black marks (from cheap runners) just the slightest swipe with acetone will clean just about any mark. And I can just hear the gasps and bodies hitting the deck in a dead faint over anyone using acetone on vinyl rubber. However, if you're quick and only use a small amount of acetone, you can get away with it.
Now, none of this is worth doing UNLESS you follow up with something to protect the vinyl after you've cleaned it. Most automotive rubber and vinyl cleaner/protectors will work. I use Meguiar's vinyl & rubber cleaner / conditioner. As a cleaner it's a hopeless failure but as a protector, it's not half bad. I use it because it seems to last about 5 minutes longer than the automotive products.
Once you use the protector, it's makes the next cleaning job much easier.