I am in the process of finishing a tub/shower combo with a showerhead on each end and one in the middle of the ceiling. I currently have wonderboard on the three walls surrounding the tub, and the ceiling and plan to apply Kerdi on all surfaces and then tile over the kerdi. My question is about the transition between the tub and the walls. The tub has a factory installed flange on each side that has a wall. Is it enough to just tile down to the top of the tub tub and then use silicone caulk between the tile and the tub? Or should I bond the kerdi to the tub using caulk/kerdi bond in addition to the caulk between the tile and the tub?