By positive displacement I mean that the volume changes as in a piston engine.
To get a good vacuum you have to compress the remaining gas to extract it whilst a vacuum cleaner is just a fan.
You also have to remember that the force from the vacuum is proportional to the area at that vacuum and that the maximum force is about 14 lbs per square inch.
You may be better served with some gasket material at the edges of the boxes so as to get a good seal.
Hope I am explaining it ok.

Peter