Good - planning out in detail the design with all correct mesurments
Bad - Winging it with minimal design details(trust me on this one
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Freekin awesome - feeling when your done!!!
Melamine is definatly good - freeking heavy though if your building big enclosure like I did.
Make sure to take into concideration what you are planning on having inside the cage to determine dimentions, bigger is always better.
Have fun and don't be afraid to ask questions on here !