I was wondering the same thing...I have a 55" Samsung. But after doing some research, I learned a couple things...forgive me if I'm repeating things you know:
1. Most of the soundbars that are that slim in height do not have quality sound
2. You get better sound if the soundbar is placed above the screen rather than below for a couple reasons (one being you can have a larger speaker with larger drivers, etc.
With that I did some more digging and found some people have made neat brackets that bolt to the back of the TV (much like a wall mount system would mount to it). The brakets simply come up the back of the TV and then they ran a horizontal piece across the width of the TV that connects to the two vertical pieces. Then you can mount the back of the soundbar to this horizontal piece. Some people just used the flat metal pieces you can get from Home Depot/Lowes/Menards/etc....they are cheap and come with holes already in them, etc.
Hope this helps...it's what I'm planning to do.