My ULS has the honeycomb table, and all it really has under it is about a 2 inch gap. The light diverges enough before it hits the bottom so it doesn't burn the paint off. The downside is that if debris collects down there, the diverged beam IS still hot enough to set it on fire.
Black anodized aluminum has worked well for me in the past - once you get away from the focus point, it just absorbs the energy.