Seems that your mind was already made up to use 3/8. You can rarely go wrong with the next size up. To save a couple of pennies you will be very foolish, and most likely very sorry in the long run. But, they are your pennies. You have been given excellent advice you would be wise to take it!

Best wishes.

: My thoughts were that since its a straight shot from the manifold to the fixture, there is a lot less pipe. In my case maybe 30-40 ft of tubing going to one fixture. 3/8 is rated for 2 1/2 GPM.