Thank you so much, everybody.
That helps a lot.
If you still want input, the MAY 2015 Consumer Reports has info on mattresses and in particular they mention two companies Casper and Tufts and Needle that have good/interesting return policies.
"...you get 100 nights to decide whether to keep it. If not Casper will let you exchange or return it for your money back with no restocking or other fees. Shipping is free, too."
re Tuft and Needle "it has a 30-night trial period. No mattresses actually go back to the company; instead, you're asked to donate it to a charity and show the seller the receipt for a full refund - or full credit toward an exchange. ..."