We just put in a stainless steel shower pan and walls - much lighter than tile would be and no plastic.
Where are you thinking of using drywall?
There really isn't any application I can think of that would be recommended...as your trailer moves down the road the drywall would turn to dust from normal movement over time. Most interior "walls" are wood or wood/vinyl over particleboard, plywood or masonite. Besides, normal stick-frame construction type walls take up a lot of valuable floor space. In an Airstream, every inch is treasured.
Shari
