due to noisy thudding neighbours above me ,im about to frame below the existing plasterboard ceilings,put in accoustic rockwool bats and 12mm plasterboard.my spans are about 3-4metres,can anyone tell me if i can use 3x2 cls at 400mm centres even doubling up every second joist if i have to, to save me the extra inch in height,or am i better just using 4x2 cls for my framing? all replies mucho apprieciated,cheers-dan 
