I have heard that it is not good to mount an amp to a sub box because of vibration, but I have limited space to place the amp will this damage the amp??
you can use L brackets to screw or bolt the box down inside the trunk. or just go straight through the bottom of the box itself. depends on box and all though. just watch out for wires, lines and the fuel tank.
the good thing to do justin would be to get a peice of wood and stick it to the box and then on top of the perice of wood, put some foamy stuff to absorb the vibrations so your amp doesnt. then mount the amp on top of the foam type substance.
i had to mount one of my amp to the box cause of space too. so i mounted on a piece piece of board first and i put a couple of layers of edead on the board. after that i used locking washers for each of the four screws that i used to mount the amp to it.