Just make sure that there will be NO vibration or your bezel glass will rattle!
Idea #1- You may want to consider cutting a rectangular hole and use screen door material (fiberglass) from Home Depot for your speaker grills. This would give you a speaker grill that will allow the sound to pass through unmuffled. You could get GameDork to make you some small, custom metal frames with a lip for the screen door material. This would allow you to recess the grill frame into the rectangular hole in the bezel glass. The lip would go on the outside of the bezel glass. Think of how a button mounts into your CP, that's the general idea.
Got a pic of your cab to share? This would give a better idea for us, of your size contraints.
Idea #2- You may be able to mount them horizontally above the monitor. Less work, $$$, time, etc.
Nice speakers BTW. I tried them out at either Best Buy or Office Depot & Liked them.
Scott