I believe the PC is rated to about 22 litres, but you can get away with a larger vessel if it's insulated (and giving the PC a hand by filling it with hot water, so the preheating doesn't take as long certainly helps).
You simply need to employ a little common sense - for example I wouldn't fill a 22 litre vessel with packages of frozen filet mignon, then add water to displace all of the air between them and then drop the PC in and expect it to be successful cooking them in a reasonable amount of time. (indeed, it would take quite some time for such a bath to come up to temperature - if it ever did, because of such a high ratio of food vs water - the circulation would be quite poor).
You want the water to circulate well and you want your food to have uniform exposure to the water so it cooks evenly (which is why for many things such as steak and ribs, we often utilize sous vide racks). While they reduce the sheer number of items that you could cook in the vessel simultaneously, they provide spacing to ensure your food cooks evenly.
If you wanted to do many items on a frequent basis, you may want to acquire a larger camper-style cooler, place two sous vide racks in it and cut a whole in the lid for your PC. (and also preheat it with hot water...maybe some from a kettle as well, just to minimize the preheat time). Something I could see a caterer doing.