Hello, Can anyone tell me if a 3/4 thermostatic valve is the correct choice (vs the 1/2 model) when used with both a shower head and a hand held shower unit? Each shower head will be controlled by volume control. Not sure about whether to use 1/2 or 3/4 inch for the volume controls. The hot and cold water feeds are 1/2 inch. My water pressure is 50PSI with a flow rate of 7 GPM. If I was to use the 3/4 inch parts should the piping be 3/4 inch or reduced to 1/2 bwtween the thermostatic valve and the volume controls?