Hello The Net:
additional considerations:
1. Add a small hole in the bottom to allow the box to vent, << 1/8" drill is OK. small enough to keep the bugs out, but enough to prevent a vacuum build up inside or over pressuring.
2. Not all electrical boxes are created equal. The cost effective (cheap) ones are PVC. Some use sheet metal type (self tapping) screws to secure the cover. The better ones use a metal insert that mates a machine screw. The threads last longer. Some PVC material is softer than others that are more brittle. Be careful drilling holes.
3. Typical NEMA ratings are #12 for indoor wet environment, 4X for weather proof/tight. Newer IPC ratings are available but you need to research the IPC #'s. I avoid NEMA 12 enclosues
4. Ebay can be your friend for cost effective larger weatherproof enclosures. Search electrical enclosures. For fiberglass enclosures, BONDO fiberglass filler is easily applied to fill existing holes. Tape over the back side, fill with BONDO, paint to seal.
Other enclosures are available in fiberglass ($) aluminum ($$) and stainless steel ($$$$). Some with stainless steel hinges and latches to open the cover.
5. design for your environment. Here in New England we have temperature extremes and lotsa rain/snow/wind. A milder environment like So. Cal. will allow a simpler box. I avoid painted steel boxes, even the galvi ones...
6. Another source after Home Depot and Lowes can be www.TekSupply.com a agricultural supply house. Electrical supply houses for tradesmen can also be helpful.
Stan, W1LE FN41sr Cape Cod