When replacing the carpet probably with laminate flooring how do you deal with underneath the slide out? That and the engine cover seem to be the only problems to replacing carpet.
I assume since you are asking about the engine cover you are talking about a gasser with a doghouse. No real way that I can fathom to cover that with anything but carpet or soft vinyl and not sure I would do anything other than carpet. The noise deading qualities of carpet over the engine would lead me that way. As for the material under the slide, it really depends on your coach and slide type.