On a whim i drilled 3 2" holes on back of the mustang 1 to see if it would improve the tone.. it did in spades and effects like delay come alive. It gets rid of the boxiness in tone and let's the amp breathe giving more articulation, depth, and makes the tone's sound like they are coming from a much bigger speaker.... Just used a 2" holesaw blade with a drill on the back board lower left and right corners and up a tad in center for the 3rd hole.. the 2 port's on left and right should be adequate though.