Ah, the curse of Class C's. I'm not sure if there is anything you can do short of being more selective on the driveways you choose to navigate. I've found that taking them slowly and at an angle (where possible), mitigates somewhat the clearance issue. Some folks put on the urethane wheels but that actually makes it worse by reducing your clearance by a couple of inches. :S
Our 24 footer isn't too bad, when we do touch it is the bottom of the Reese hitch that scrapes which sounds a lot worse than it is. We've seen a lots the 30 something footers not only drag their tails but actually get hung up. Watch out for the large concrete tire stops often found in CG's as they don't budge when challenged by a mere Class C. :B