I am roughing in a Rohl shower (thermostatic valve) that will have two functions: One shower head with volume control, and one handheld shower with volume control.

Since there is no tub, can I use that mixer port for one of the other functions, or am I supposed to tee off the upper port toward each volume control? I know there is higher volume from the tub filler port, but wondering if there's a reason not to do this for another function since they each have their own flow restrictor anyway.

The hot and cold supplies are 1/2" (not the 3/4" that is recommended).

Also, the handheld will be on the far side of an adjacent wall (interior wall) at a higher level level than the mixer and the other volume control. Any recommendations on the configuration of that piping? If I can pipe from the tub port of the mixer, can it just travel over and then up into the volume control valve, or do I need to loop upward for any part of it?

Thanks very much.