Farm tractor seats, Im not familiar with the current models. I have seen a spring aluminum seat, that I believe will eventually crack and break. Its built in the shape of a U laying on its side. Box style bases are probably the best mounting mechanism.

There are other strut type posts that either use air or gas and may or may not have a secondary coil spring. Those units are taller and often set up to use on bass boats.

Air seats for commercial trucks are capable of doing the job, but sharp jolts can bottom out the seat, which is a slaming motion on the spine.

Unless youre a guide, Id look at the third option. Its very high tech, but cheap. Go to your Les Schwab tire store and order an 8 inch inner tube for the smallest trailer tires or wheel barrows. Inflate it about half way. It will keep your tailbone off the point of impact. If you have an extremely large build, get a 10 or 12 inch.