OK -- I'm a bit confused about the Grotherm Thermostatic valve and how I am supposed to install it with the volume controls. There are two inlets -- one hot and one cold, and two outlets, one to the shower and one to the tub. This is going in a tub & shower application.... I thought that one volume control / shut off would go in-line to each fixture (one to the shower and one to the tub) from each outlet. But, when I talked to the plumbing supply house to confirm, they told me that I should cap the bottom outlet, T off the line coming out of the top, install the valves off the T, send one line up to the shower and one down to the tub. This seems a bit odd to me as it requires some creative in wall plumbing to get everything to line up. Other showers I have done were not nearly this complicated. Is this correct? Any advice?