I would fill each chamber only until the diffusors are under water, but just a little bit, to ensure maximum bubbling.
I tried the bong with less water. just very slightly above the percolators, just like you suggested.
This indeed makes the vape more "airy". very smooth indeed. Also i think the high is stronger.
I thought more water is more filtration and cooling. But I just needed more air, less water.
Still feel light irritation on the throat sometimes. But that could be because, the whip of my extreme q
needs replacement, which i will replace tomorrow after i pimped it with glass-screened arizer elbows.