Brewman,
I e-mailed marquis and they said that a sub-base if done correctly was fine. I've since e-mailed them back to find out what exactly this means. I've had the Hot Spring dealer and Saratoga Spa dealer say using 2 inch pavers are fine. I was hoping to hear from someone who has successfully used this method to see what they did in terms of their foundation (how deep there sub-base was and what it is made of.)
According to my e-mail the foundation will not effect the warrenty ..."the reason that we suggest it (4 in concrete base)is not so for the warrenty as we feel even if you put in directly on the ground it would be fine for the warranty period, but over the long haul 10, 15,20 yrs you may have issues."
Eventually, we will put a deck on to include an area for the tub. We can't afford both right now and I really need the therapy that the hot tub gives verses the deck!