You could simply change to an "AIRPOT" thus allowing you to fit more plants on the floor.
You could use 6litre airpots or 15litre airpots. Grow your plants so they finish under 3ft after stretch and with the 6litre airpots you could fit maybe 8 plants under your 1 600w still with 4oz per plant quite easily.
I was getting around 3.5oz per plant with new strains all the time.
Im an ex coco grower. Do you use Trichoderma or mychorhizal fungi in your coco? Beneficials to aid root growth and nutrient uptake.
J