Soakguy:
Here's how Midway did it on my Galaga:
They routed out the side edges so that there's a "lip" that the door fits in and rests against without falling "into" the inside.
The key latch keeps it from opening out.
The bottom of the door panel has a "tongue" which fits in a groove at the bottom.
So you put the bottom in, then swing the top into place, lock the lock and it all holds in place.
The main reason I am against hinging the door, is that whenever you need to get in there you'll have to move the heavy cabinet far out enough to swing that door open. With a removable back, you just need to move it out a foot if you need to quickly grab something...