So, one shower with dimensions of about 8' x 3'. Want to put two shower heads in on opposite walls. I don't need two temperature controls. I would also like to be able to turn both of them on and off from a single location.

Builder wants to use two mixers and have two independent showers. I don't like the look of two shower controllers on the same wall. No one seems to sell a shower controller/valve plate that is small. Why are they all 7" or so?

Anyway, talking to Delta they tell me that their standard T14440 mixer is rated for a flow of 6.5gpm at a PSI of 60. So, why couldn't a diverter provide enough pressure to supply 2 shower heads at the same time? The gpm drops to around 5 at around 40PSI, which would still be able to supply two shower (even if the restrictors on them accidentally fell off).

So, what am I missing? What's the hesitation from the builder? Am I just being dense here and there's some really good reason to have two mixers and two different feeds?

Home is brand new construction, shower is on 2nd floor, it's not on a well. I guess I can ask what the pressure is at the meter. Would the pressure at the meter equal the maximum pressure I can have in the house? I haven't thought about pressure and fluid dynamics since college and am trying to get up to speed as quickly as possible.