Just curious: Why is hard cover how you're building your spa decision around? Not against it, mind you, just an odd way to go about looking at spas. I used to sell Tuff Spas and they're a neat tub, but I haven't found a brand that is in the Hard Cover market that - when assessing quality - can line up enough with a more traditional spa.
I am sure a Strong, Tuff, Eco, etc. dealer can maybe speak more about it, but you're usually getting low-end in parts / equipment / build technique.
Thus - Hard cover and High quality spa don't seem to be possible. Sorry if I am nay-saying and I am not knocking them in any way (again - I used to sell them) but their whole point is (paraphrasing) to not be acrylic, and not be high dollar, and to be sold at shows.