Ebb and Flow 4" rockwool

Will i need a coco mat?
I'm going to use 2x4 flood table with as many 4x4 rockwool cubes as will fit.(appx 50). Would I need a coco mat under? What are pros and cons of having one?

The cocomat is great. The downside is they arent reusable (although good in garden planters or the chicken coop) and you can reduce the daily cycle time or frequency because it holds more water. The pros are you get nice root mat under it and the best is they hold the pots down when the table gets flooded so they dont end up sideways.
First though I would cap the top so that the flood zone and roots aren't exposed to the light before buying the mat. A layer of gravel will do just as well. I wouldn't pay full price for the mat that's for sure.