Tboooe - visited the Mondo site. Not exactly sure which product of theirs you bought...those triangular traps? The Roxul is a dense but cuttable unfinished sound absorbing product. Can get it at Lowes. If there is room within the Mondo product you could maybe add the Roxul to give another layer of thickness. There is some acoustical info on the Roxul product in the PDF file here:
http://www.roxul.com/files/RX-NA_EN/pdf/SnS%20Sheet_Eng.pdf
http://www.roxul.com/files/RX-NA_EN/pdf/SnS%20Sheet_Eng.pdf