Flood and drain on 40ft long tables sounds and looks more difficult to me,(for even water distribution at exactly the same amounts of uptake the tables would have to be perfectly level, and a recirculating system is more finicky than DTW. Plants take what they want when the need it so the res would have to be monitored way more closely, and then what did the plant eat? your missing 300ppm of what nutrient?Thats I plan on using high frequency fertigation with varying shot sizes/dry back times(growth stage dependent) depending on what the plants are asking for. I need ph swing or flux for proper nutrient uptake Mo absorbs best around 5.5-5.7ph Ca and Mag 6, I want as much control as possible, and dont feel flood and drain is where its at for such a large scale