How do you stabilize your Class C when parked for camping?

I don't. I can life with what little movement I feel. Compared to a similar size TT, a C motorhome is built on a much sturdier frame, and has much more mass compared to the mass of people moving around inside. 200-300 pound guy rolling around in the overhead bunk can make things move, probably still would if you put down scissor jackes at the corners or used leveling jacks to lift the frame off the wheels.