Is there anything to keep the roots moist during the off time? Most recirculating drip-ring systems I've tried and know of either run 24/7 or have at most 15-minute breaks between watering to prevent the roots drying out and dying. Usually, the more you water the better your results.
I love innovation and people who try new things, but the whole idea of trying different things is usually to find out what works best that hasn't been tried before.
Obviously I'm curious about the reasons behind your set-up and what you're hoping to achieve. Maybe if we all have a better understanding of that, we can try to help out by sharing experiences.
For example, if you really want to a run-to-waste system - and not a recirculating system - then I can understand a bit more why you are doing things the way you are. Of course, coco works much better in run-to-waste systems, but there might be a compromise with your system to make it work better than it is. Don't get me wrong - it is working the way it is - but we all like to make things better . . .
One tip I can offer is to use a bypass valve or tap to control your flow, like this one:
The way to set it up is similar to the diagram below. Ignore the arrows for a minute and imagine the shutoff valve in this diagram is your pump and the grass/ground is your reservoir. The pump pumps nutrient solution from the reservoir up to a T section, where one branch goes to the grow (right pipe) and the other to a tap (left pipe or "faucet"). Water takes the path of least resistance, so if you turn the tap on, water will flow out of it back into the reservoir. If you turn it off, the full force of the pump will go to your plants. If you turn it half-way, you can control the amount of flow. I do exactly this with my set-up (will try to take pix later). The water diverted back into the res has the added bonus of creating a waterfall effect which aerates your nutrient solution - which is why I don't run bubblers in my tank.
The other advantage of using a control valve is that as your reservoir runs low, gravity (the weight of water on top) does not assist the pump as much, so you find the water pressure from your pump drops as the water level in your res drops. This also makes it hard to control the exact flow. With the bypass system, you simply turn the tap off little by little to decrease the bypass and increase the pump flow to the plants. It would be quite easy to create a 24/7 drip system this way that drops just enough nutrient solution to feed your plants and keep the roots moist (in a "drip, drip, drip" way), while allowing your reservoir to hold enough water and also create a true run-to-waste system where the runoff is disposed of, but is not too excessive.
A bypass valve also allows you to control water flow without continually trying to guess what pump size you need for different applications.