In reply to goldmember: I've got an old inner tube wrapped around mine, stops any chain slap noise when I'm belting down through the woods :p
You can get clear tape called heli tape on ebay, tough, cut to size, and clear so you'll not see it. Don't know what rules you're on about but can't see how that would be illegal. Also might be good to put the bottom of your downtube to protect against stone chips.