Weight shouldn't be a problem, but depth could be. I have the same problem, my center is 38lbs. and is about 3x the width of the top of the TV. I used some speaker spike cones without the tips to raise it up, and keep it in place.
There are stands available that can help support the speaker. Sanus makes one, the TV-SB I think, and another company makes an even simpler one than that, that might do the trick. You want the center pulled out to the edge, or even hanging over just a bit, from the front edge of the TV.