HUH?
How do you think that will help...???...
...and especially
behind the LCD?
Look...if you are going to put up foam and then put up hard/reflective shit on top of it to reduce the muffled sound...
...well then, just rip out some of the damn foam!
I really DON'T want to give you more band-aids for that foam mess, as I think you need to reevaluate your entire setup...
...but maybe what you call "muffled", is really just "dead" sounding, so try adding a touch of reverb to those vocal tracks and see if that helps when you mix them with the music.
But I still think you need to get out of that foam coffin....save it only for "must-use" situations, and try to do your tracks out in a more open/live space.
I think RAMI is right...you are in denial, and determined to stay the course with that foam booth. You may end up recording stuff in there and eventually get it to sound almost OK...but in the end...IN THE END...you will find out that the foam booth is not the way to go if you want to improve your audio quality.