You think having groves to keep water in the table is good? I thought you’d want all the water out to get oxygen to all the roots?The risers in my flood and drain fittings raise the flood level 35mm. I have used 1 and 2 and did not notice any difference in yields. If you lift the lid and watch during a flood what you will see is the roots all floating around in the nutrient, especially during the first few weeks of flower. Then when it drains they all just follow the laws of gravity. And thats why proper flood trays are good because they have the grooves and hold some water between floods.