Ermm.... head spinnin'.

I think you're missing... um... well,... let's take another route.

Forget the math... let's go with the "why".

The reason you're filling up the water level xx-inches below the netpot, is because you don't want to drown your roots...
So, you place your plants yy-inches into the hydroton/rockwool/choped-neutrons medium, and place that hovering OVER your water level... not touching.

Now, your air bubbles should rise to the top of the water line, and "pop".
When they "pop", they will "spray" the bottom of the netpot with small water dropplets... enough for wetting the medium... the plants growing, and dolphins singing.

So, it doesn't really matter if you're placing a plant 5 inches into the medium, then hovering above the water line...
Or if you're placing a small clone 0.5inches into the medium, then hovering...

It's the pops I tell ya'... the pops

Please let us know if this helped anything at all, or just made matters worse. We appreciate your feedback.