TL;DR
Turret range + or - depending on them being on top or bottom of a cliff.Turret Range & Cliffs
I'm suggesting adding a bonus to turret range when placed above a cliff, in the direction of "down the cliff". And a reduction in turret range when placed at the foot of a cliff & trying to fire "up over" the cliff.When above:
![Image](https://forums.factorio.com/images/ext/40fddb1f23c37088ff20fd87f8a2d757.jpg)
When Below:
![Image](https://forums.factorio.com/images/ext/ff85ae7c9c333c72e4bb62167f4835fe.jpg)
or something along these lines