Diddo the get them as far from brush as possible.
The best precaution against HOWR is to locate the box more than 30 m away from any shrubs (I know not always possible in small lots). HOWR love shrubs. I found a study that showed boxes within 20 m were almost guaranteed top have some sort of HOWR interference at some point, and HOWR usually nested within that 20 M zone (no boxes were IN shrubs for this study) but that the further from shrubs the boxes were placed the less “interference”. eggs were pieced in boxes placed 20 to 30 m from shrubs but no HOWR nesting occurred. 30 m seemed to be the distance after which there was no “incursions”. This is generally similar to what I am seeing with the boxes I’ve placed in parks. Its just one study but certainly worth keeping in mind. If you can then place the box further than 30 m from shrubs, can save huge amounts of stress for you.
The study also found that the EABL preferred to nest around 30 m away from trees (chose the boxes first in the study) so it works out well for the blues to have boxes away from the shrubs.
Can’t find the article at the moment but it is online somewhere…was focused on TRES but had HOWR and EABL included. (I love that they did not just throw out all the data related to non-target birds! So valuable!)