Replying to my old thread. The tub and cover I posted about in 2016 were replaced under warranty due to a bubble appearing in the acrylic, that was a heck of a fight with Caldera.
Now in 2022, I was in need of a new cover again. After a bit of research I went with
https://www.thecoverguy.com/Price seemed fair, it arrived to my home in about 5 seeks, I upgraded to the weathershield fabric instead of vinyl, and it makes for a very light cover.
I've only had it a little over 2 months so no clue on longevity in the AL sun, but rain and moisture roll right off it. Nice so far.