I'm getting ready to set my tub in my bathroom in a few days. It's a Sterling Accord tub with the "caukless" three piece wall kit. They recommend using their provided felt pad for install, or if one is not available, to set in a base of mortar. I'm assuming since they mention the latter in official literature, that doing so would not void the warranty, but why the felt pad as the number one suggestion? The base of this tub is VERY stout and has reinforced ribbing and really sturdy support feet. Would I still be susceptible to creaks down the road if I forewent the mortar mix?