Consider using an interior fan in conjunction with your window air conditioner to spread the cooled air more effectively through your home without greatly increasing your power use.
A fastener in sheet metal should not be any closer than four to six diameters from the next one. For example, if you are using a 1/8-in. Pop Rivet, the nearest another rivet should be is between 1/2 to 3/4 in. By using this rule, you will reduce the chances of damaging a part, as well as make optimum use of your fasteners.