I have pretty good WiFi in my home (3 access points), so I wasn’t able to detect any signal attenuation (signal strength stayed „excellent“)
Originally my plan was to have the extender PCB mounted bare to the enclosure, but there wasn’t a convenient mounting point on the PCB. Instead I added standoffs to the lower plastic case. After that, I put the cover back on because the plastic tabs on the cover keep the extender PCB in place.
If you have a convenient way to mount the extender PCB direct to the case that would make things cleaner. Given all the experiments/hacks I did before getting my enclosure, this was the easiest (incremental) path for me.