Questions/advice on new pontoon seat.

Hello: I just purchased a Scadden pontoon for lake fishing. It is a Cardiac Canyon with 12" pontoons. Thinking about buying a new seat and need some advice:

1. Any advice on a seat with good back & ass support?
2. Is it worth installing a swivel?
3. If so what height would be the best?
4. Does the swivel need to lock in place?
5. Where should I look to purchase all items so they mate up?
6. Do I need a pressure gauge?

Thanks in advance for your replys. Dan Bromley, Grand Junction, Co.