the counterlung location just changes how much of a difference there is..Depends on where the counterlungs are locatedOTS will act different than backmounted.
This is why..
when we inhale our chest expands displacing more water than when we exhale, so on oc this makes us more buoyant than when we exhale, on a closed loop system ther is another gotcha, all this gas gets moved to some breathing bag which is MORE flexible than our chest, so the amout of expansion in our chest is generally less than the expansion of teh breathing bags.. on ots lungs in the prone position we are exhaling to a higher pressure than our chest cavity do the extra expansion is a bit more limited, on back mounted c-l we are exaling to a lower pressure than our lung centroid so the expansion is a bit greater than if the lungs were at chest level.. Body positioning will determine the exact effect..