Homemade Street Light

This is my home made street light... As you can tell its simple, the reflector is a dog bowl which has a nice shiny coating on the inside. It has a pulse rated socket holding a older Sylvania 70watt HPS bulb. The rod holding the light to the pancake electrical box is only threaded on the ends making a nice clean pipe in between. The wire is rated for 600volt and has quick disconnect connectors in the bowl above the socket to connect the socket to the wire which goes to the plug which then connects to the ballast. So there are no wiring connections in the pancake electrical box. On the pancake electrical box there is a hole drilled in the top for a hook to go through to hold the fixture up and a hole on the bottom for the wire to go through. As you can see there is a piece of wood behind the lower half of the electrical box, that is there just to prop the light up higher. - - - I am using a F-Can 70watt HPS ballast, but as you may know that is not made to be exposed to the elements. I would would like to make a outdoor/elements/water proof ballast box. I was looking into a 6x6x4 thick plastic (or what ever they are called) box, but I am worried the ballast might get to hot or the box would melt? I would like to use a 50 or 35watt HPS ballast but just don't know what type of box to put it in? What do you think? Give me your input! Thank You!