I would go for not overfeeding at all, the nutrients that are not eaten by the plant acumulates in the soil.
Last run I never gave more than 700 ppm and when I tested the runoff it had between 1100 and 1600 (different strains, same food).
I know it is good for them having different kind of nutrients available, but for instance if there’s still a lot of Nitrogen in the soil in the flowering stage, that’s not good at all. Fortunately, in DWC you have a better control and you can change the whole nutrient soup when you wish. Counting the days to go back to DWC 
, cheers … 