The worst rattle I had was form the screen door. The panel in the very bottom was just loose enough to drive me bonkers. A bead of silicone around the frame shut that bad boy up.
Having a C, I have had a squeak from the seam between the cab and coach for several years now. From the drivers seat, it seems to come from directly behind my left ear. I pulled the trim of the wall, and pried the cover panel back, then removed each lag bolt one at a time looking for ANYTHING that could possibly indicate a source. Nothing found.
I started looking down the wall farther, and think there may be a broken screw below the floor. Trouble is, that the generator is right in the way and must be removed to access that part of the wall. I found that I can make is better by jamming a piece of rubber between the coach and cab near the base of the door.
I also had a rattling vent flap for the stove. The outside flap was held in place(closed) with only one tab (original design) and was exactly where turbulence from the front at highway speeds seems to vortex. I had a small piece of foam to hold the flap down until I finally replaced the hood for a better design. As a side note, I found that the old hood was the culprit for the water leak that caused the delamination I now have.
Besides that, a few felt bumpers applied on the cupboard doors and I ride fairly quiet.
My most useful tool was having the better half drive while I roamed around with a notebook and noted where sounds came from.
Joe