I use a similar set up. The only problem is that water can get into the PIR. It is best to take it apart & use Silicon around the seams. I have shot 23 foxes since Jan 1st from my attic window with it.
The amazing thing is that if you miss them, that they still come back. Even the most lamp shy foxes are shootable, as I can fire within a second of turning on the light as I have the rifle aiming at the exact point the fox is on before I turn on the forestock switch. Usually they take 2 secs to react, i.e eyes to vulpine brain "what the bloody hell is that red light ?".
Vulpine brain "Its one of those lights that is associated with a big bang & the disappearance of your Missus, I think that we should get out here fast".
Brain to legs "lets get out of here fast". This takes about 2 secs for a fox to cognate.
Hopefully I can interupt its thought processes with a 3200 fps 95 gr 6.5 V max before the brain to legs message gets passed.