I have a Riva 510 with Boge 2.0 cartos. I just bought some yummy juices from Liberty FLights but have noticed that when I take a hit, I get a slight crackling noise..... is the crackling noise when you take a hit normal?? I'm assuming it is? When the mild crackling noise during a hit is not present, it usually seems to mean it's under-filled. It IS better to over-fill than under-fill, correct?