MIMF

Hello everybody, my name is Matteo Baratella, I am from Italy, I am trying to build my first guitar cabinet for the Marshall AVT150H pre-amp head. (150 watt output - impendence 4/8 ohm). My cabinet is 70 x 70 x 30 cms = 27,5 x 27,5 x 11,8 inches with a thickness of 1,8 cms = 7,08 inches. My question...