I cut a piece of 18mm MDF to wth width of my cab, routed out a shape at the bottom to allow access to the ports on the bottom of the monitor then drilled holes that lined up with the VESA mount on the back of the monitor and bought some 4mm machine screws. The MDF is secured into the cab by screws that go into 32mmx32mmx150mm blocks that are screwed into the cabinet at each end.
If/when the monitor fails, it can be removed by removing the MDF from the rear of the cab with the monitor still attached. Remember to consider how you're going to take it out of you need to. It would be easy to mount a monitor but have no method of removing it after the cab is finished.