Sounds like you have a good set up of houses – however, I would question the one house which you have facing west, as this is facing the hot sun in the summertime. Might be okay for the 1st nesting. I believe your boxes facing southeast are much better – here in Mid-Missouri I believe SE is away from prevailing winds, which is what is recommended – mine are all facing SE. I have had no experience with anything other than wooden boxes (cedar, which have lasted 8+ years & still going) – this “indestructible plastic” box you have – does it not get terribly hot? If you have your boxes up early (January of February) I bet those blues will be scouting them next season. Good luck.