Advice on parking pad size

I have bought into a piece of land near the coast to have a home base for fishing and will be leaving my 5th wheel part-time. It’s a 42’ 5th wheel and I have to make a decision in the next couple of days on a concrete pad size. l’m thinking 14 x40 would be big enough to allow my steps to stay on the concrete ( solid, fold down kind) and a foot or so on the opposite side. No way I can afford a pad big enough for my truck and camper to sit on. Any advice?