I am replacing a 30"x60" tub/shower combo with a 40"x72" soaker tub. Lets use north for the front of thek existing tub where the drain is located. The new tub has the drain in the center by the front side (east). My drain piping is cast iron, and runs south under slab to main drain line about 6 feet. The distance from the new drain location to the old is about 2 feet. Can i get by with building up where the tub will sit and connecting new tub to old drain without busting concrete? Sorry i do not have any illustrations, i am posting from my ipad.