Pax has a smaller inside diameter than copper when you will turn on the spout your showerhead will also be dripping if you read the manufacture instructions it will say do not use pex for spout level 2.
Why no pex for tub spout drop.
Copper keeps the spout in place.
Any restrictions cause the water to gently back up as it waits its turn to exit the tub spout.
There is no way to secure pex adequately to keep a tub spout from flopping around.
The interior diameter of pex is actually a fraction smaller than copper this forces water to come out of the shower at the same time as the tub spout.
Shark bite copper shark bite 90 iron pipe pex everywhere else.
You cannot use pex because the pipe coming out of the valve needs to be able to support the weight of the tub spout and handle the abuse of pulling pushing down of the divirter built into the spout.
Valve drop to spout tube is within the 6 11 inch tolerance.
With a built in diverter you could use a pex drop eared ninety degree female adapter and a nipple but that is more trouble than it is worth.
Pex when you pull up on the diverter the entire spout moves.
Long story short it is unacceptable.
Eventually the line reaches the shower head and one gallon of water will exit there for every 4 or 5 that comes out the tub spout.
So it s fine to have 1 2 pex going to the shower head.
The tub spout can be copper brass or galvanized pipe.
There is no stacking issue with the.
Valve to tub spout tube is.