Due to the following change in 0.16.20 this crashes:
"Renamed render_layers: ground_patch, ground_patch_higher, ground_patch_higher2, and air-entity-info-con to ground-patch, ground-patch-higher, ground-patch-higher2, and air-entity-info-icon."
Here is a fixed version: http://cyanox.nl/Additional-Turret-016_0.2.1.zip (its really just a small edit)
