What's generally considered a best practice in terms of directionality of the eyeballs for returns in terms of them being pointed towards skimmer and towards water surface or deeper?
With my rectangular pool, which has 2 shallow end returns, 1 deep end return, and 1 deep end skmmer, I have the two eyeballs in the shallow end pointed 45 degrees towards the deep end, and the one return in the deep end directly across from the skimmer points directly at the skimmer.
In terms of how high/low they are, they were pointed downward just enough so you didn't see any water movement on the surface of the water.
However, I noticed the other day after a bunch of pollen landed on the waters surface that the pollen didn't seem to be moving around the pool towards the skimmer very effectively (although, to be honest I'm not sure what should be visible in this regard). So I pointed the eyeballs up towards the waters surface so that I could see the water being moved by the returns, but not high enough to calls the return water to break the surface.