I have gutted my bathroom and want to replace a previously tiled shower with a drop-in Am Standard oval garden tub with self-supporting feet. (This tub is also sold as a whirlpool, so has under-deck clearance.) One installer has said that the existing center shower drain can be plumbed above the slab to connect to the right-drain tub; and another installer says no, the slab must be broken to a depth of two feet to re-route the drain. Are both of these methods feasible, but one preferable; or am I contemplating hiring someone who doesn't know what he is doing?