If the cabin is a pier and beam structure, perhaps you can run some static load tests by reacting against the weight of the cabin. Perhaps you can detach the pile from the structure, clamp a pair of brackets on the pile, and set jacks on the brackets reacting against the beam. If the beam is continuous across several piles, it may provide resistance quite a bit higher than the normal static load. In areas of expansive soils, houses are often underpinned by jacking steel pipe piles to refusal and reacting against the structure.