I have found it difficult to use PAPI lights in X-Plane 11. The lights are somewhat useable at night, but during the day it's very difficult to read them.
You can adjust them by editing the lights file:
BILLBOARD_SW VASI3 1.8 -0.9 0.5 0.5 1.2 1 6 0 0 0 0 1
In my case, I have changed 1.2 to 12. I'm still experimenting with it, but I feel it has made a difference.