I dont think of the net as something to hold the plant or canopy down. The net can do two things for you.
In a SOG situation it can help support the plants, and keep heavy colas from falling over.
However, I think its best use is in a SCROG. In that situation, the main purpose of the net is that it lets you train or force the stems to grow sideways instead of up. That does two things. It spreads the plant out horizontally and fills the space from side to side and front to back - assuming you train it properly.
However, the most important thing that sideways growth does is that all those sideways growing stems will put out new vertical stems from each and every node. Every one of them will become its own new cola full of buds.
But wait, there's more....you can take those new vertical growths, and force them to grow sideways too - and they will also put out new vertical stems from each node. In no time at all you can have dozens of colas instead of a few.
Im growing a single plant at the moment under a scrog. I havent counted them, but I think I must have 50 or 60 colas with some nice buds growing. Im expecting to get plus or minus a pound from a 28"x38"x48" tent - from a single plant.
This is by far the worst job I have done as far as training under a scrog. I completely misjudged the stretch and didnt get the canopy very even, but you get the idea.
Thats not to say you are doing anything wrong with your grow. Your canopy looks great - better than mine by far. Its just that you have more of a sog than a scrog.