Most everyone you talk to always likes the WEBSTER model for just your camping family. I went with the COLEMAN ROADTRIP which comes with a nice wheeled tote and has several different cooking tops. It also has the water reservoir that collect all of the grease coming from the cook tops and makes for very easy cleanup...
Easy setup that uses the 1LB propane canister
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Cooking for 20 people will take a pretty big cooking setup perhaps a 50-gallon barrel cut in half and welded up frame...
Something like this perhaps...
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Roy Ken