I am not an expert by any means. But I thought MH's should be a little lower han that. Like a few inches from the top of the tank. And maybe a fan blowing across the water to keep it from heating the water to quickly.
The light looks very bright. I just figured you would want to focus as much of the light in the tank.
If I am wrong it will be a learning experiance for me. I need to get a MH myself. I know nothing about them, but what I see and read on this board.
Good luck. I am sure your corals love it.