I am in the process of finishing the plumbing of a master bathroom. I decided to use PEX for the supply lines. I intend to make my own manifolds out of copper so I can zone the house. Right now the whole house is fed with 1/2 copper from the meter, eventually I plan to replace that with 3/4 PEX to the manifolds. My question is should I use 1/2 or 3/4 copper fitting to build the manifolds and why?