help with new glass top and light

Hello all,

I have a 29 gallon tank that is starting to get pretty heavily planted :-)
I know that my single 24" light that came with my perfecto hood is not
enough light, so I got a perfecto glass top and a double strip today. I
don;t think I have it installed correctly though.

There was a small tab that looked like it would be fastened to the center of
the part to lift up for feeding and maintenance, sit hat what it is for?
Also, it seems like I cannot lift that half all the way without bumping the
new double light fixture, and the glass top seems to sag in the middle. It
fits inside the lip of the tank, but the glass top is up a bit where I
installed this handle.

Should I be looking at a replacement glass top from a better source? Any
ideas, suggestions etc..would be appreciated.

Thanks,

Zach