Dehumidifier Wye duct sizing

Using the Aprilaire 1870 as an example, it is rated at max 310CFM through a supplied back flow dampered 10" supply duct.

I need to split that - 50/50 - into two separate HVAC supply plenums.

What should the size of the WYE splits be: 10" or 8" or...?

Thanks,

Pete

source https://hvac-talk.com/vbb/showthread.php?2224066-Dehumidifier-Wye-duct-sizing&goto=newpost