I'm tiling our bathroom, some basics - floor: 3/4" OSB T&G, 12" I-joists, 16" on center, new construction. I'm using the Schluter/Ditra-Heat uncoupling membrane but no heat cable under the tub that will be going in. The tub: Kohler slipper tub with four 1" dia. stainless legs and a composite skirt around the base, hiding the legs. The tub weighs 500 lbs. empty and holds 70 gallons of water. The floor tile is 18"x24". My question: with the tub full plus an occupant (two if I'm lucky), it will weigh in the area of 1350 pounds. Each leg will be supporting around 350 pounds. Will the tile over the DItra support this weight without cracking? Should I cut out a 3" circle through the Ditra where each leg will go and fill in with thinset, then tile over it to support the extra weight? Am I being paranoid? Thanks in advance!