Metal Halide with glass top

[darknessheir]

Hello I currently have a 48 in power compact fixture that is 260 watts total. It takes up about half of the tank top. The tank has a glass top and then the light sits directly on the glass with the canopy on top. I want to purchase a clamp on metal halide thats about 150watts and clamp it on the back to help boost the light in my tank. I am just wondering if I will have any problems with the glass top breaking or trapping to much heat. I have a sump with fans which helps with evap and cooling. Just dont want to buy this metal hallide and have my tank have to be topless becasue I have a 4 yr old. Need canopy thus the glass top!