Ive made sunbrella fitted seat covers for a truck before, but didnt remove the factory cover. They worked well and held up decent.
We i dont think there should be any issues, we made tons of boat seats and cushions out of sunbrella

Sunbrella makes upholstery fabrics for outdoor furniture. You may want to consider using it. It has many of the same properties as their boat cove material.

Yes it was outdoor furniture fabric that they were interested in, I wasn’t quite sold on the idea but it may look ok in a smaller quantity. I brought up resale might be difficult if it is a real outlandish pattern, but they said they Enjoy the car and had no plans to sell any time soon.

I have used it on patio furniture and porch furniture. A little on the stiff side but it has held up fine outdoors for 3 years on my own outdoor chairs.(I bring them in in the winter, but they are out in the sun and rain half the year).

Sunbrella has an outdoor furniture fabric that is softer than the marine canvas.

We often work with sunbrella fabric and it is quite dense and doesn't stretch at all. I mean, if you use it on the central parts of the seats (those that have a flat plane form), then you can use it, but if you need minimal stretching, then you will have huge creases that cannot be removed

I do a lot of marine canvas and upholstery with Sunbrella. Yes anything with complex curves or contours will create wrinkles. If you have a heavy duty steamer like a Jiffy then a lot of wrinkles can be steamed out like a dream. Heads up incase you've never tried to steam Sunbrella.

Do you have photo of your work with Sunbrella fabric seats? Show me please how it looks like in this fabric :wink:

Looked thru my photos and couldn't find any Sunbrella covered seats other then one I did years ago with wrinkles thru it. Learned a lot since then about Sunbrella. I might have misunderstood though. Were you interested in Automotive or Marine Seats covered in Sunbrella??

I would have no problem using sunbrella for an automotive application if it was a new foam job (Firm w/ minimal complex curves). Otherwise I'd never use it. I can say now its very durable for work applications in rear seats. Especially for hunters with dogs or other heavy use applications. I live in a big farming and hunting region. Eastern Shore Maryland