Welcome, glad you are here.
Have to take off the ceiling panels? ; Pajamas kitty, Eugene mouse, myself and a few other eight legged friends have all lived full time, and happily in this bus for over 9 months now, and we never removed a single panel. Just sayin.
Also i am not a rust hater, so long as it isn't effecting the frame or suspension, i figure a few rusted holes allow more oxygen in when buring the wood stove. Besides Eugene needs quick escape hatches with Pajamas on duty.