I wouldn't.. "Slosh the tank"? Idk what that means, but fuel sloshing around in a 5L tank is one reason why I would prefer a small tank and refilling from the spare bottles. There's no need to use a 5L tank for more frequent short journeys anyway, so it would be a pain to put a different tank on the night before going on an unusually long trip. Oh and I can imagine that a 5L would be more difficult to attach securely on top of the top tube. As you said, it's nice to stop and stretch too.