Reason why I asked is because I've tried a dual showerhead before and it sucked ass. It was completely useless unless one of the nozzles was off.

I'm just curious if you know the answer: does the regulator attenuate the pressure downwards even if the overall pressure is below the target? Say the pressure at the spigot is 100 psi, but legally must be at 40psi, so the regulator attenuates it down to 40. If you divide it into the two shower heads, will the regulators simply attenuate it down to 40 psi, or cut it down to something like 20 psi?