I used to own an Olson 911S which came equiped with an Origo 2 burner stove. The stove worked great and seemed to heat water just fine. Cooked some fairly gourmet meals on it too. I filled the canisters while at see using an old cleaned tuna can with a number of hole punched in the bottom with an awl. If I remember right, it was about 5 holes about 1/16" in size. The tuna can just fit into the opening on top of the canister. I measured how many tuna cans it took to fill the canister. Made filling at sea much easier. I don''t remember how many cans it took for a fill.