A couple questions about Ditra uncoupling membrane. First, for you guys with real world experience with this, does Ditra really noticeably work in preventing cracked tiles and grout lines? I know every situation is different, but on the whole, does it work as promoted? And second, they recommend modified thinset from subfloor to membrane, and unmodified from membrane to tile? Why is this required, there must be a good reason. Thanks.