Hello Slide, I have not used Sallies myself, but I know how they are intended to work with Sound Lab and if you have more specific question I am happy to explain. I am not exactly sure what your goal is. Your ears should be the best solution to your specific room. Understanding how the sound emanates from the front of Sound Lab (45degree) dispersion and then how the sound then exits the back of the panel is also helpful to think of positions (there is a conversion point behind the speakers where sound will focus at one point)
The photo shows what I use – not exactly a Sallie, but a cylinder diffuser with a layer of absorbing material (I plan to improve on this, but mostly it these are hidden from view) They are positioned where the conversion of sound meets strongest behind the speaker.