I'm setting up the rough plumbing for an alcove bathtub. The American Standard tub supports 1 1/2" plumbing. My plumbing is No hub Cast iron. Is it acceptable to bump up the ptrap , santee, etc to 2" with either a No hub 2x 1 1/2"coupling or 2x 1 1/2" reducer fitting? The bump up would occur in the vertical pipe coming out of the bottom of the tub. Thanks!