The use of "marine grade upholstery" has amazed me for many years. It is never 100% water proof, fades/discolours quickly and rips with ease.
Of equal amazement is that buyers put up with it by accepting that it is the best fabric available yet only a few inches from the seat is a fabric that is many years durable etc etc ---- yes the tubes.
Hypaoon is expensive,
say retailing at £45 a m but it lasts and when packed onto closed cell foam will last as long as the tubes. So when buying a new boat ask the manufacturer to fit the seats with offcuts of the hypaolon. They will charge and you may not get the fancy piped edges but is will be a pukka job.
We fit it, we charge for it, yet not a single customer has disagreed with our principle of longetivity.
For a retro fit buy from say Henshaws or Polym and it is in most cases a diy or supply material to your local upholsterer.