I have a eurobraced tank with 2.5 inch bracing all the way around the top that is flush with the top glass sides etc. One method I am considering is to have the glass top in two pieces with a hinge down the centre. This way access would be either by lifting the front half or by lifting the back half. The lighting hood I am making will be wood, and weigh about 20 lbs. The two halves of the glass lid will have a urethane foam insulating strip on the side facing the tank. The light hood will likewise open from the front and back. The light hood will rest on the glass lids when not raised. This way, the lids will be held down all around the perimeter and sealed flush with the tank due to the foam strip. This is of course only possible if there are no skimmers, cords or pipes that have to enter the tank from the top. One I get the lid done, I will post a couple of pictures.