Great question. Most of acoustics performance in general is about coverage area, ie, how many square feet of a given treatment are we adding to the room? So the short answer is, more is better. I usually recommend start with at least 4 Scopuses to begin to discern improvements.
The other part of this is, placement on these devices is very very important, ie, they need to be in a "pressure zone" in the room for the tuned frequency in question. This can take time and experimentation for sure......
