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If you sand off the back two corners of the cam wheel, and add a chamfer to the lip of the box, the cam would rotate when closing but not while opening. This would allow the box to close if you accidentaly nudged the dials while it was open.
If the intake for dust was in the bottom it would force the air to rise vertical and help separate dust using gravity. Like a reflux still. This would increase filtration (clogged filters filter better, but "suck" less). This same action would put some major strain on your vacuum. The cyclone effect is useful because it separates without restricting the flow as much.The dust is falling out of the path, not back into the path to get sorted again.