Here is a calculator that Scott Morell has developed to assist you in building your own "High Profile" aquarium canopy. The high profile canopy is at least 14 inches tall and has plenty of room to place your lighting system even metal halide. There are options for access doors on the ends of the canopy and an option to have the back open or completely closed.
All you need to do is enter the actual length and width of the tank and the height you want the canopy/hood. A materials list will be calculated and displayed on the following page along with assembly instructions.
Disclaimer:
Construct these canopies at your own risk. The authors and GARF will not be responsible for any damage or injury caused by improper construction. The combination of wood and water can lead to serious consequences, so please use common sense or consult a professional carpenter if you do not have the proper experience.