I didn't mount the light. I know it looks like it is, but if you look closely, you can see that the light is actually just sitting on top of the lid. Doesn't make much difference. I have to use the lid because those sponge filters really splash around. The lid does a great job of keeping the water "in." I am also using a small box underneath the refugium for support so the whole weight isn't hanging on the edge of my tank. These 6.6 bookshelf units are made of plastic and that's a lot of extra weight hanging back there. I found that the box that the mini powerhead came in supports it nicely and elevates the back side of the refugium a little so that the water level isn't so close to the edge.
One other nice thing about these is you get that extra gallon of water in your system with these small tanks. Every little bit helps keep things stable. Now if they only made one with the inlet on the other side, I could run dual refugiums, bwahahaha!